Primary gastrointestinal lymphoma

Abstract

Gastrointestinal tract is the most common extranodal site involved by lymphoma with the majority being non-Hodgkin type. Although lymphoma can involve any part of the gastrointestinal tract, the most frequent sites in order of its occurrence are the stomach followed by small intestine and ileocecal region. Gastrointestinal tract lymphoma is usually secondary to the widespread nodal diseases and primary gastrointestinal tract lymphoma is relatively rare. Gastrointestinal lymphomas are usually not clinically specific and indistinguishable from other benign and malignant conditions. Diffuse large B-cell lymphoma is the most common pathological type of gastrointestinal lymphoma in essentially all sites of the gastrointestinal tract, although recently the frequency of other forms has also increased in certain regions of the world. Although some radiological features such as bulky lymph nodes and maintenance of fat plane are more suggestive of lymphoma, they are not specific, thus mandating histopathological analysis for its definitive diagnosis. There has been a tremendous leap in the diagnosis, staging and management of gastrointestinal lymphoma in the last two decades attributed to a better insight into its etiology and molecular aspect as well as the knowledge about its critical signaling pathways.

Key Words: Gastrointestinal lymphoma; Epstein-Barr virus; Helicobacter pylori; Celiac disease; Diffuse large B-cell lymphoma

INTRODUCTION

Gastrointestinal tract is the most common extranodal site involved by lymphoma accounting for 5%-20% of all cases[1]. Primary gastrointestinal lymphoma, however, is very rare, constituting only about 1%-4% of all gastrointestinal malignancies. Gastrointestinal lymphoma is usually secondary to the widespread nodal diseases. Although virtually lymphoma can arise from any region of the gastrointestinal tract, the most commonly involved sites in term of its occurrence are the stomach followed by small intestine and ileocecal region[2]. Histopathologically, almost 90% of the primary gastrointestinal lymphomas are of B cell lineage with very few T-cell lymphomas and Hodgkin lymphoma. Certain histological subtypes have been noted to have a relative predilection site as mucosa-associated lymphoid tissue (MALT) lymphoma in stomach, mantle cell lymphoma (MCL) in terminal ileum, jejunum and colon, as well as enteropathy-associated T-cell lymphoma (EATL) in jejunum, and follicular lymphoma (FL) in duodenum with a geographic variation in its distribution[3]. Multifocality, however, has been noticed particularly in MALT lymphoma and follicular lymphoma. Certain risk factors have been implicated in the pathogenesis of gastrointestinal lymphoma including Helicobacter pylori (H. pylori) infection, human immunodeficiency virus (HIV), celiac disease, Campylobacter jejuni (C. jejuni), Epstein-Barr virus (EBV), hepatitis B virus (HBV), human T-cell lymphotropic virus-1 (HTLV-1), inflammatory bowel disease and immunosuppression[4,5]. Marker expression and translocations of common histological types of gastrointestinal lymphoma are depicted in Table 1.

Table 1 Expression of common markers and translocations in histological subtypes of gastrointestinal lymphomas.

Type	CD5	CD10	CD19	CD20	CD22	CD23	CD43	CD79a	CD3	CD7	CD4	CD8	CD30	CD15	CD45RO	Additional features
Diffuse large B-cell lymphoma	-(+)	-(+)	+	+	+	-	-	+	-	-	-	-	-(+)	-	-(+)	Bcl-6+(-), Bcl-2+(-), t (14;18), t (3;14), t (8;14)
MALT lymphoma	-	-	+	+	+	-	-(+)	+	-	-	-	-	-	-	-(+)	t (11;18), t (14;18), t (1;14), t (3;14)
Follicular lymphoma	-	+(-)	+	+	+	-(+)	-	+	-	-	-	-	-(+)	-	-	Bcl-2+, Bcl-6+, t (14;18)
Burkitt lymphoma	-	+	+	+	+	-(+)	+	+	-	-	-	-	-	-	-	C-myc, t (8;14)
Mantle cell lymphoma	+	-	+	+	+	-	+	+	-	-	-	-	-	-	-	Cyclin D1+, t (11;14)
Peripheral T-cell lymphoma-unspecified	+(-)	-(+)	-	-	-	-	+(-)	-	+(-)	-(+)	+(-)	-(+)	-(+)	-(+)	-(+)	-
Extranodal NK/T cell lymphoma	-(+)	-	-	-	-	-	+	-	-(+)	+(-)	-(+)	-	-(+)	-(+)	-	EBV+, gains of 2q, 15q, 17q, 22q, losses of 6q, 8p, 11q, 12q, 13q
EATL	-	-	-	-	-	-	+/-	-	+	+	-(+)	+(-)	+(-)	-	+(-)	TIA1+, gains of 1q, 5q, 7q, 9q, losses of 8p, 9p, 13q
Hodgkin disease	+(-)	-	-	-(+)	-	-	-	-(+)	+(-)	-(+)	-	-	+(-)	+(-)	-(+)	Variable

+: ≥ 90% positive; +(-): > 50% positive; -(+): < 50% positive; -: < 10% positive cases. MALT: Mucosa-associated lymphoid tissue; EATL: Enteropathy-associated T-cell lymphoma; EBV: Epstein-Barr virus.

Dawson’s criteria are used for labeling primary gastrointestinal lymphoma, that include (1) absence of peripheral lymphadenopathy at the time of presentation; (2) lack of enlarged mediastinal lymph nodes; (3) normal total and differential white blood cell count; (4) predominance of bowel lesion at the time of laparotomy with only lymph nodes obviously affected in the immediate vicinity; and (5) no lymphomatous involvement of liver and spleen[6]. Ann Arbor staging with Musshoff modification is commonly employed to stage gastrointestinal lymphoma and the international prognostic index has been used to define the prognostic subgroups and Paris staging has increasingly gained its significance. Accurate diagnosis and staging of gastrointestinal lymphoma are detrimental for the stratification of treatment in this heterogeneous group of malignancies. The different procedures employed for the pre-treatment staging include endoscopic ultrasound (EUS), endoscopic biopsies, computed tomography (CT), magnetic resonance imaging (MRI), 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) or molecular markers[7,8]. Contrast-enhanced techniques and functional imaging such as perfusion CT can also help the monitoring, assessment, and prediction of response. New promising techniques such as hybrid PET-CT imaging and new PET tracers like 18F-fluoro-thymidine may significantly benefit the overall management of lymphomas[9].

In the following sections, the commonly involved sites of gastrointestinal lymphoma and its clinical, pathological and radiologic features are discussed with stress laid on the different histological subtypes based on the predilection. The characteristic features of gastrointestinal lymphoma in different regions of gastrointestinal tract are shown in Table 2.

Table 2 Characteristic features of gastrointestinal lymphomas.

Region	Age (yr)	GIL (%)	Sex	Predilection site	Etiological/risk factors	Presenting symptoms	Common pathological subtypes	Radiographic features
Oropharyngeal	> 50	-	M > F	Tonsil, nasopharynx1, base of tongue	EBV	Dysphagia, dyspnea, painless mass, ulcer, oral/hearing pain, B symptoms rare	DLBCL, EMZL/MALT, PTCL, FL, MCL, ENKL, HD	Lobular mass, ulcers
Esophagus	Variable	< 1	-	Mid and lower third	EBV, HIV	Dysphagia, odynophagia, weight loss, epigastric/chest pain, pneumonia, bleeding rare, B symptoms rare	DLBCL, MALT lymphoma, HD, MCL, T-cell lymphoma	Stricture, ulcerated mass, submucosal nodules, varicoid-like, achalasia-like, aneurysmal, fistula formation
Stomach	> 50	60-75	M > F	Antrum	H. pylori (MALT lymphoma), HTLV-1, HBV (DLBCL), EBV, HCV	Epigastric pain, dysphagia, nausea, vomiting, weight loss, abdominal mass, gastrointestinal bleeding, obstruction, perforation, B symptoms rare	DLBCL, MALT, PTCL	Ulcers, polypoid mass, thickened fold, mucosal nodularity, linitis plastica-like
Small intestine	Variable	20-30	Usually, M > F	Ileum, jejunum, duodenum, multiple sites	Celiac disease (EATL), C. jejuni (IPSID), EBV, HIV/AIDS	Abdominal pain, nausea, vomiting, weight loss, GI bleeding, obstructive symptoms, intussusceptions, perforation, diarrhea (in IPSID), B symptoms rare	DLBLCL, MALT, EATL, MCL, Burkitt lymphoma, FL, IPSID, PTCL, ENKL	Polypoid mass, multiple nodules, infiltrative form, ulcer, excavation, fistulization, extraluminal mass, mucosal thickening, strictures
Colon/rectum	50-70	6-12	M > F	Caecum, ascending colon, rectum	Celiac disease (EATL), EBV, H. pylori (MALT lymphoma)	Abdominal pain, weight loss, abdominal mass, lower GI bleeding, obstruction, perforation	DLBCL, MALT, EATL, MCL, PTCL, Burkitt lymphoma	Polypoid mass, ulcers, mucosal nodularity, cavitary mass, mucosal thickening, strictures, aneurysmal

¹Included here though usually not applicable. GIL: Gastrointestinal lymphoma; EBV: Epstein Barr virus; DLBCL: Diffuse large B cell lymphoma; EMZL: Extranodal marginal-zone lymphoma; PTCL: Peripheral T cell lymphoma; FL: Follicular lymphoma; EATL: Enteropathy-associated T-cell lymphoma; MCL: Mantle cell lymphoma; IPSID: Immunoproliferative small intestinal disease; HD: Hodgkin’s disease; HTLV-1: Human T-cell lymphotropic virus-1; HCV: Hepatitis C virus; HBV: Hepatitis B virus; H. pylori: Helicobacter pylori; C. jejuni: Campylobacter jejuni; HIV: Human immunodeficiency virus; AIDS: Acquired immune deficiency syndrome; ENKL: Extranodal NK/T-cell lymphoma.

CLINICAL/PATHOLOGICAL/IMAGING CHARACTERISTICS

Oropharyngeal lymphoma

The head and neck region is the second most common site for extra-nodal lymphoma accounting for 10%-15% of all cancers in this region. Approximately 2.5% of all malignant lymphomas originate from the oral and paraoral region, and the majority of them in the Waldeyer’s ring include adenoids, palatine tonsils, base of tongue and oropharyngeal walls. Tonsil is the most frequently involved site (> 50%) of tumors, followed by nasopharynx and base of tongue[10]. Several factors are known to increase the risk of oropharyngeal lymphoma including EBV. The affected patients are usually at the age of over 50 years with a predilection of males. The most common clinical presentations of oropharyngeal lymphoma include airway obstruction, hearing pain, progressive enlarging painless local mass, dysphagia and foreign body sensation in the throat. Cervical lymphadenopathy is present in over 50% patients with tonsillar lymphoma[11].

More than 80%-90% of oropharyngeal lymphomas belong to the B-cell lineage of non-Hodgkin lymphoma (NHL)[12]. Diffuse large B-cell lymphoma (DLBCL) is the most common type of primary oral and paraoral NHL with a small percentage of thymic T-cell type. Histologically, DLBCL, composed of intermediate-large cells which may be noncleaved, cleaved and immunoblastic, shows B-cell lineage with expression of pan-B-cell antigens (CD19, CD20, CD22, CD79A, and PAX5/BSAP), and is less commonly positive for germinal centre cell markers (CD10 and BCL6) and negative for T-cell antigens. A small number of cases show a translocation between the BCL-2 gene on chromosome 18 and the IgH gene on chromosome 14, t (14;18)[13]. Other lymphomas involving the Waldeyer’s ring include 15% B-cell lymphomas in extranodal marginal zone of MALT, 8% peripheral T-cell lymphomas, 6% follicular lymphomas, and 3% MCLs. Hodgkin lymphoma (HL) involving the oropharynx is very rare accounting for about 1%-5% of all Hodgkin diseases. The majority of oropharyngeal HL are of lymphocyte predominant and nodular sclerosis type on histopathology with a common immunophenotype of Reed Sternberg cells positive for CD15, CD30 and negative for CD45, CD20, and EMA, which can rule out the diagnosis of NHL[14].

Radiologically, oropharyngeal lymphoma typically appears in barium studies as a lobular mass near the base of tongue in the palatine fossa with the overlying mucosa usually being nodular. The appearance of oropharyngeal lymphoma can be hard to differentiate from more common pharyngeal carcinomas. Because the signal intensity of lymphoma is similar to that of normal tissue, the MR signal characteristics cannot reliably show the early lymphomatous involvement at these sites. CT or PET with FDG and CT (PET/CT) has proved their usefulness both in diagnosis and staging of the disease and in assessment of its response to therapies[15]. Certain features that may favor the diagnosis of NHL on imaging are the short clinical history and a large homogeneous mass which displaces rather than invades local structures and large homogeneous non-necrotic cervical nodes[16].

Esophageal lymphoma

The esophagus is a rarely involved site, accounting for < 1% of all gastrointestinal lymphomas. Esophageal involvement usually results from metastasis from cervical or mediastinal lymph nodes or extension from gastric lymphoma. Primary esophageal lymphoma is extremely rare, with less than 30 cases reported in the literature[17-19]. The majority are the DLBCL type of NHL. Only few cases of MALT lymphoma, MCL, T-cell lymphoma and HL involving the esophagus have been reported[19-22]. The etiology of esophageal lymphoma is unknown and the role of EBV in its pathogenesis is controversial. It has been shown that esophageal lymphoma is most common in immunocompromised patients, with HIV infection as a probable risk factor[17]. The age of presentation is variable. The common symptoms of patients with esophageal lymphoma include dysphagia, odynophagia, weight loss, chest pain or present as a result of complications such as hemorrhage, obstruction or perforation with a tracheoesophageal fistula. Constitutional B symptoms (fever, night sweats) are not typically present.

Almost all cases of primary esophageal lymphoma are DLBCLs with positive surface markers of tumor cells on immunofluorescent staining for immunoglobulin G and κ light chain. MALT lymphoma of the esophagus, however, unlike that of stomach, is not associated with H. pylori. HL of the esophagus is extremely rare. Follicular lymphoma affecting the esophagus is a part of multifocal presentation in the gastrointestinal tract.

Radiological and endoscopic findings in esophageal lymphoma vary greatly and are nonspecific, which poses diagnostic challenges when it is differentiated from other benign and malignant lesions. Radiographic patterns of esophageal lymphoma, described in the literature[18-20], include stricture, ulcerated mass, multiple submucosal nodules, varicoid pattern, achalasia-like pattern, progressive aneurysmal dilatation, and tracheoesophageal fistula formation, and none of them is diagnostic. The morphological features seen at endoscopy are nodular, polypoidal, ulcerated or stenotic[21]. EUS has gained clinical acceptance for the assessment of lymphoma and preoperative staging, because it can accurately depict the structural abnormalities and depth of invasion of the lesions. EUS findings, however, are not pathognomonic, with presentation varied as anechoic, hypoechoic or even hyperechoic masses[22]. CT findings in esophageal lymphoma are nonspecific and not diagnostic, with features such as thickening of the wall mimicking other common tumors, such as esophageal carcinoma. CT, however, they are valuable for the evaluation of the extraluminal component of esophageal mass, its mediastinal extension, fistula formation, and status of lymph nodes, thus playing a role in staging disease, assisting in stratification of available treatment modalities, evaluating treatment responses, monitoring disease progression, and detecting relapses[23]. Recently, incorporation of PET/CT has emerged as an indispensable tool in staging the disease and following up the patients with extranodal involvement of Hodgkin’s and non-Hodgkin’s lymphoma, with an increased sensitivity and specificity. Diffuse large B-cell non-Hodgkin lymphoma of the esophagus is manifested as circumferential thickening of the wall, with diffuse increased FDG uptake. However, the intensity of FDG uptake in lymphoma is influenced by various intrinsic tumor factors such as histological features and grade, as well as various extrinsic factors. FDG PET/CT can also detect the indolent lesions that are undetectable on conventional cross-sectional imaging[24].

Gastric lymphoma

Stomach is the most commonly involved site (60%-75%) in gastrointestinal tract followed by small bowel, ileocecal region and rectum[25]. Gastric lymphoma accounts for 3%-5% of all malignant tumors of the stomach[26]. Although the incidence of gastric carcinoma has been reduced, the incidence of primary gastric lymphoma is increasing[27]. H. pylori play a role in the development of most MALT lymphomas. However, its exact mechanism has not been fully understood, although a chronic inflammation may enhance the probability of malignant transformation via B cell proliferation in response to H. pylori mediated by tumor-infiltrating T cells[28]. H. pylori may play a similar role in development of DLBCL and few studies have shown complete remission after eradication therapy alone[28]. It has been shown that individuals with positive HBsAg have an increased risk of developing NHL[29]. It was reported that HBV plays a role in the development of B-cell NHL[30]. In contrast, primary gastric lymphoma with a T-cell phenotype is relatively rare, accounting for only 7% of primary gastric lymphomas in HTLV-1 infected endemic areas and a relatively large number of such cases are secondary gastric involvement of adult T-cell leukemia. Primary gastric T-cell lymphoma without HTLV-1 infection is rare, and sporadic cases have been reported[31]. The age of most gastric lymphoma patients is over 50 years with a relative predilection in males. Clinical symptoms of gastric lymphoma are nonspecific and indistinguishable from other benign and malignant conditions. The most common complaints of gastric lymphoma patients are epigastric pain, weight loss, nausea and vomiting. Occasionally, an abdominal mass is palpable. Lymphadenopathy is rare and its patients often have no physical signs. Perforation, bleeding, or obstruction is very uncommon. Unlike nodal lymphoma, B constitutional symptom is not common.

Although all histological kinds of nodal lymphoma can arise from the stomach, the majority of them are of the B-cell origin, and MALT lymphoma and DLBCL account for over 90%. MALT lymphoma comprises up to 50% of all primary lymphomas involving the stomach. Histologically, the most significant finding is the presence of a variable number of lymphoepithelial lesions defined by evident invasion and partial destruction of mucosal glands by the tumor cells. MALT lymphoma shows the immunophenotype of B cells in the normal marginal zone of spleen, Peyer’s patches and lymph nodes. The tumor B-cells can express the surface immunoglobulin and pan-B antigens (CD19, CD 20, and CD79a), the marginal zone-associated antigens (CD35 and CD21, and lack CD5, CD10, CD23) and cyclin D1. MALT lymphoma can be divided into H. pylori positive or negative based on the presence of H. pylori. H. pylori negative MALT lymphoma tends to have a higher positive rate for t (11;18) (q21;q21) translocation than H. pylori positive MALT lymphoma[32]. DLBCL, a heterogeneous group of tumors which are clinically, histologically, immunophenotypically, cytogenetically variable, can be divided into 3 subgroups, namely germinal-center B-cell-like, activated B-cell-like, and primary mediastinal DLBCL according to the gene expression patterns with each having a different prognostication. The most commonly seen translocations as mentioned earlier include t (14;18) (q32;q21) with BCL2-rearrangement, t (3;14) (p27;q32) with BCL6-rearrangement and t (8;14) (q24;q32) with MYC rearrangement, respectively. Variability has been observed in CD45, CD5 and CD10 expression, with the CD10 expression in particular referred as a prognostic indicator[33].

Endoscopy cannot distinguish gastric lymphoma from the more common gastric carcinoma. The three main patterns that can be recognized at endoscopy include ulceration, diffuse infiltration, and polypoid mass, which are, however, not specific[34]. Endoscopy, however, is an indispensable tool for the initial diagnosis and follow-up of cases as well as for obtaining biopsy specimens. EUS can assess the extent of lesion and its invasion. Lesions are usually hypoechoic although few hyperechoic cases have been reported[34]. Infiltrative carcinoma tends to have a vertical growth in gastric wall, while lymphoma tends to show mainly a horizontal extension and more involvement of perigastric lymph nodes[35]. EUS is highly accurate in detecting the depth of lymphomatous infiltration and the presence of perigastric lymph nodes, thus providing additional information for treatment planning, and can differentiate lymphoma from carcinoma both in early stage and in advanced stage[36].

Radiographic patterns of gastric lymphoma observed in double-contrast UGI studies include ulcers, polypoid mass, thickened fold, mucosal nodularities or infiltrating lesions, which are not conclusive, thus posing a diagnostic challenge while differentiating from other malignant and benign lesions, hence requiring pathological confirmation. Preservation of gastric distensibility and pliability, despite the extensive infiltration with gastric fold thickening, is a finding more suggestive of lymphoma. Gastric wall thickening is much less severe in low-grade lymphoma than in high-grade lymphoma on CT images, and abdominal lymphadenopathy is less common in low-grade lymphoma. Preservation of the fat plane with no invasion of surrounding structures may be suggestive of lymphoma, although it is, however, not specific. Transpyloric spread and extension of lymphadenopathy below the renal hilum and the presence of bulky lymph nodes are more suggestive of lymphoma than carcinoma[37]. The patterns of gastric involvement observed can be segmental or diffuse infiltration, or localized polypoid. Tumor infiltration is usually homogeneous although areas of low attenuation may be present in larger tumors. Diffuse infiltration involving more than 50% of the stomach and segmental infiltration are the most common features of gastric NHL on CT images[38]. The MRI features include irregularly thickened mucosal folds, irregular submucosal infiltration, annular constricting lesion, exophytic tumor growth, mesenteric masses and mesenteric/retroperitoneal lymphadenopathy. The tumors are usually homogeneous and intermediate in signal intensity on T1-weighted images. Heterogeneously increased signal intensities are noted on T2-weighted images. The enhancement is usually mild-moderate after intravenous administration of gadolinium dimeglumine[39]. Application of 18F-FDG PET/CT in diagnosis of gastric lymphoma is challenging due to the physiologic FDG activity in the stomach and variability in the degree of uptake in various histologic subtypes. It was reported that aggressive gastric lymphoma has more intense uptake than low grade MALT lymphoma[40].

Small intestine lymphoma

Primary malignant tumors of the small intestine are very rare, accounting for less than 2% of all gastrointestinal malignancies. Lymphoma constitutes 15%-20% of all small intestine neoplasms and 20%-30% of all primary gastrointestinal lymphomas. Ileum is the most common site (60%-65%) involving small intestine lymphoma followed by jejunum (20%-25%), duodenum (6%-8%) and other sites (8%-9%)[41]. The age of presentation varies with the histological subtype of lymphoma. The clinical presentation of small intestinal lymphoma is non specific and the patients have symptoms, such as colicky abdominal pain, nausea, vomiting, weight loss and rarely acute obstructive symptoms, intussusceptions, perforation or diarrhea[42].

Primary small intestine lymphomas that are more heterogeneous than those in stomach include MALT lymphoma, DLBCL, EATL, MCL, follicular lymphoma and immunoproliferative lymphoma, and can be divided into immunoproliferative small intestinal disease (IPSID)[43]. IPSID, also known as alpha chain disease, is a MALT-associated lymphoma due to C. jejuni infection and characterized by “centrocyte like” mucosal infiltration with plasma cells that secrete monotypic and truncated immunoglobulin, a heavy chain lacking of an associated light chain. IPSID mainly affects older children and younger adults with a predominant involvement of proximal small intestine, the symptoms of its patients are diarrhea and abdominal pain[44]. MCL primarily affects individuals at the age of over 50 years, and involves terminal ileum and jejunum appearing as numerous polyps, hence called multiple lymphomatous polyposis[45]. The prototype MCL is positive for pan B-cell antigens, although few cases of CD5-MCL have been reported[44]. Cytogenetic analysis of MCL has shown the rearrangement of bcl-1 locus on chromosome11 due to t (11;14) (q13;q32) translocation, accompanying cyclin D1 antigen overexpression. Few cases of cyclin D1-negative MCL, however, have been reported with up-regulated cyclin D2 or D3[46]. Burkitt’s lymphoma mainly affects children and is associated with EBV and HIV/AIDS[47]. T cell lymphoma of the small intestine accounts for approximately 10%-25% of all primary intestinal lymphomas primarily occurring as enteropathy-associated T cell lymphoma, and most of them are often complicated by Crohn’s disease[48,49]. Although follicular lymphoma is very rare, it expresses SIg (frequently IgM) and pan B-cell antigens with CD10 and bcl-2 expressed in almost 90% of cases. It is negative for CD5 and cyclin D1 differentiating it from MCL. IgH/BCL2 rearrangement with t (14;18) (q32;q21) can be demonstrated by FISH or PCR analysis in the majority of cases[50]. Lymphocytic lymphoma (chronic lymphocytic leukemia) rarely arises primarily from the gastrointestinal tract.

Evaluation of the small intestinal lymphoma has been revolutionized since the introduction of capsule endoscopy (CE) and double-balloon technique of push-and-pull enteroscopy which is capable of enabling biopsies as well as performing interventions, and limiting major surgical interventions. Small intestine lymphoma appears as a mass, polyp and ulcer on CE which cannot be distinguished from other lesions[51]. Radiologic findings of small intestinal lymphoma are not specific, thus posing a difficulty in distinguishing it from other benign and malignant lesions. The common features of small intestine lymphoma seen in barium studies and CT include polypoid form, multiple nodules, infiltrative form, endoexoenteric form with excavation and fistulization, and mesenteric invasive form with an extraluminal mass. The radiological findings usually do not correlate to its pathological subtypes. Certain features are, however, peculiarly noted. MCL, follicular lymphoma and MALT lymphoma rarely present with multiple polyps (multiple lymphomatous polyposis)[52]. Burkitt lymphoma usually presents as a bulky mass in the right lower quadrant. IPSID tends to affect proximally with a disseminated nodular pattern leading to mucosal fold thickening, irregularity and speculation. EATL, usually proximal or diffuse, shows nodules, ulcers or strictures[53]. PTCL preferentially involves the jejunum with an increased tendency to perforate[54].

Colorectal lymphoma

Colorectal lymphoma constitutes 6%-12% of all gastrointestinal lymphomas. Most colorectal lymphomas are secondary involvement of the wide spread diseases. Primary colorectal lymphoma is very rare, constituting only 0.2% of all malignant tumors arising from the colorectal region with caecum, ascending colon and rectum more often affected[55]. The disease predominantly affects males in the fifth-seventh decade of life with abdominal pain, loss of weight, palpable abdominal mass or lower gastrointestinal bleeding. Obstruction and perforation are relatively rare in patients with colorectal lymphoma[56].

Lymphoma of the colorectal region is mostly the B-cell lineage as other sites of the gastrointestinal tract. Primary colorectal lymphoma comprises low grade B-cell lymphoma arising from MALT, MCL and T-cell lymphoma besides large B cell lymphoma. The role of H. pylori in the pathogenesis of colorectal lymphoma has not been fully established[57]. Colorectal MALT-lymphoma is less common in colon and rectum than in small intestine. MCL in the colorectal region presents usually in the setting of diffuse systemic diseases. Peripheral T-cell lymphoma is rare in Western countries with an increasing frequency in many Asian countries, and is more aggressive in nature than other types with perforation as its common feature, and its prognosis is poor[58].

Endoscopically, lymphoma appears to be fungating, ulcerative, infiltrative, ulcerofungating, and ulceroinfiltrative types, with fungating and ulcerofungating types being more common[59]. The radiologic appearances of colorectal lymphoma are variable and significantly overlapped with other benign and malignant condition of the colorectal region. The imaging findings during double-contrast barium enema can be divided into focal and diffuse lesions. The observed focal lesions include polypoid mass, circumferential infiltration with smooth mucosal surface or extensive ulceration, cavitary mass, mucosal nodularity, and mucosal fold thickening. Diffuse lesions encompass diffuse ulcerative and nodular lesions. Peripheral T-cell lymphoma presents as a diffuse or focal segmental lesion with extensive mucosal ulceration similar to that observed in granulomatous conditions as Crohn’s disease or tuberculosis. MALT lymphoma is manifested as multiple mucosal nodularity[60,61].

TREATMENT

The treatment strategy for gastrointestinal lymphoma is dependent on the age of patients, clinical scenario, histological subtype, extent and burden of the disease, and co-morbidity, besides other factors. Surgery, chemotherapy, radiotherapy and radioimmunotherapy are the different modalities for its management and can be applied in different combinations. A detailed discussion on the treatment of all subtypes is beyond the scope of this article, thus the most common treatment modalities are highlighted in brief based on the region of presentation.

Oropharyngeal lymphoma

The definite management protocol for oropharyngeal lymphoma has not yet been established. Unlike the majority of other malignancies in this region, surgery does not play a primary role in the management of oropharyngeal lymphoma[62]. Combined chemotherapy and radiotherapy for localized oropharyngeal lymphoma is recommended in most studies[14]. Advanced oropharyngeal lymphoma is usually treated with aggressive chemotherapy with or without radiotherapy.

Esophageal lymphoma

Due to the rarity of esophageal lymphoma, no standardized approaches to its management have been formulated. Secondary lymphoma involving the esophagus can be treated with chemotherapy, while primary esophageal lymphoma can be managed with surgery, chemotherapy and radiotherapy or their combination. Treatment protocols vary depending on its histological subtypes and extent. Although surgery is the initial treatment modality, it has been recently reserved for cases with their diagnosis not possibly made at endoscopic biopsy or for those who warrant surgical intervention due to complications such as perforations. Esophageal lymphoma can be treated with local resection and chemotherapy with or without radiotherapy as its initial therapy. However, chemotherapy or radiotherapy alone can be also used as its initial therapy. The commonly employed chemotherapy regimen is CHOP in combination with Rituximab. It was reported that external beam radiation at the dose of 40 Gy can also be used[63].

Gastric lymphoma

Treatment strategies for gastric lymphoma have changed dramatically over the last two decades. However, they are still very controversial. The most widely recommended strategy for the management of early stage H. pylori positive MALT type of gastric lymphoma is to eradicate H. pylori with antibiotics and proton pump inhibitors. Antibiotic therapy can achieve a long-term remission in 60%-100% patients with localized H. pylori-positive MALT lymphoma without t (11;18) chromosomal translocation. Histological assessment of treatment response, however, faces the problem of standardization, thus mandating serial follow-up. The GELA histologic evaluation system is commonly employed at certain centers. It has been shown that monoclonal B-cells still exist in almost half of the patients despite histological and endoscopic remission following antibiotic therapy[64].

No definite guidelines have been advocated for the treatment of advanced or H. pylori negative MALT-type of gastric lymphoma. Although surgery has been used as its initial treatment, recent studies showed that radiotherapy alone can achieve a complete remission with a 5-year disease free period[26]. Thus, “involved-field” irradiation at the total dose of 30 Gy for over 4 wk has become the treatment of choice for stages I and II MALT lymphoma without H. pylori or with persistent lymphoma following therapy. Surgery is, at present, reserved only for those with complications such as perforation, hemorrhage or obstruction that cannot be treated with other alternative therapies. Systemic therapy similar to that for indolent and advanced lymphoma must be taken into consideration in patients with their disease spread. Treatment options include chemotherapy and use of monoclonal antibodies. Diffuse large B-cell lymphoma of the stomach is treated with aggressive poly-chemotherapy, which is usually combined with Rituximab. Thus, gastric lymphoma should be treated with the front-line chemoimmunotherapy with 3-4 cycles of standard R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine and prednisone) followed by “involved-field” radiotherapy. A complete remission can be achieved in advanced gastric lymphoma patients after 6-8 cycles of R-CHOP as their nodal counterparts. Recent studies have demonstrated that anti-H. pylori therapy can achieve the remission of indolent lymphoma, H. pylori negative MALT lymphoma and DLBCL[26,65].

Intestinal lymphoma

The treatment outcome of intestinal lymphoma is relatively poorer than that of gastric lymphoma depending on their histologic subtypes. Lymphoma primarily located in the small intestine usually warrants laparotomy with the affected segment removed both for its diagnosis and for its treatment. Low-grade B-cell lymphoma of the small intestine (stage IE) only requires surgical resection. Although few studies have reported its benefit for localized intestinal lymphoma particularly that of the duodenum and rectum[66], radiotherapy in particular is not beneficial for intestinal lymphoma due to the multifocal involvement and its spread. No therapeutic guidelines are available for MALT lymphoma involving the small intestine with various modalities depending on the disease burden and other clinical parameters. Local intestinal lymphoma can be managed with surgical or endoscopic resection, while some cases of colonic MALT lymphoma can benefit from H. pylori therapy alone. Multi-agent chemotherapeutic strategy is warranted for advanced stage intestinal lymphoma with multifocal presentation of MALT lymphoma. A wait and watch policy for indolent FL at stage IE is advocated by some authors until they are symptomatic or show evidence of its progression due to a comparable relapse rate in treated patients and the progression of FL in untreated patients[50,66]. Symptomatic cases, or advanced disease of FL necessitates surgery, chemotherapy (CHOP) and/or irradiation intervention. Although Rituximab is beneficial for FL, its true value has not been well ascertained[66]. MCL treatment response and prognosis are poor with a short unmaintained remission after chemotherapy. Treatment is stratified based on the eligibility of patients for stem cell transplantation (SCT). Those who are eligible for grafting are previously induced with R-CHOP or R-HyperCVAD (Rituximab, cyclophosphamide, vincristine, doxorubicin and dexamethasone). Chemotherapy regimen, consisting of Rituximab alone or purine nucleoside analogs with Rituximab, can be applied to those ineligible for stem cell transplantation. The mammalian target of rapamycin inhibitors, antibodies, bendamustine or radioimmuno conjugates, can achieve a promising outcome in patients with relapse or refractory setting single-agent bortezomib, temsirolimus and ibritumomab tiuxetan[67,68]. IPSID in early stage responds to antibiotics such as tetracycline or combined metronidazole and ampicillin, with a remission occurring within 6-12 mo. IPSID at intermediate or advanced stage responds to anthracycline-based chemotherapy, with added antibiotics such as tetracycline. Surgery plays a limited role in the majority of cases due to diffuse involvement, although it may be requited for accurate diagnosis. It has been reported that radiotherapy as an adjuvant or palliative treatment is beneficial for some cases[66]. High grade lymphoma frequently presents with complications, thus mandating surgical intervention. No optimized therapeutic protocol is available for Burkitt lymphoma which usually requires an aggressive approach. High intensity chemotherapeutic agents for a short duration, such as cyclophosphamide, vincristine, doxorubicin, methotrexate and cytarabine, can significantly improve the treatment outcome. High dose chemoradiotherapy and hematopoietic SCT are beneficial for almost 50% of Burkitt lymphoma patients[69]. Radiotherapy is not beneficial for DLBCL involving the small intestine[70]. Systemic treatment with anthracycline-based chemotherapy followed by radiotherapy is proposed for wide spread advanced intestinal lymphoma which cannot be removed. Some studies have shown that post surgery chemotherapy is beneficial for some patients[68]. The overall response of non surgical patients with intestinal B cell lymphoma to chemotherapy is better than that of those with the intestinal T cell subtype[71]. No guidelines are available for the management of EATL although anthracyclin-based chemotherapy is a mainstay treatment modality for overt EATL with a poor response. In view of the poor performance and complications related to chemotherapy, such as perforation, multimodal approaches including curative or debulking surgery are recommended to remove the gross EATL in all cases, if it is tolerable prior to chemotherapy[72]. It was reported that 66% of EATL patients undergoing surgical resection followed by combination chemotherapy and autologous stem cell transplantation can achieve a sustained complete response[73].

STAGING, PROGNOSTICATION AND RESTAGING

Staging of gastrointestinal lymphoma is a matter of debate due to various available staging systems. Although the modified Ann Arbor classification is feasible and relevant for prognosis, certain demerits in terms of disseminated and incurable infiltration of the gastrointestinal tract prompted development of the Paris staging system, which can differentiate distant lymphoma manifestations depending on the involved organ, and further subdivide lymph node involvement (Table 3)[74]. In general, comprehensive history taking and physical examination may reveal the possible etiologies of some specific lymphoma types and provide information for their further assessment and management. Minimal laboratory investigations performed include complete blood count, liver and renal function test, measurement of lactate dehydrogenase, blood glucose, serum uric acid, potassium, calcium, and phosphorus levels. Bone marrow aspirate with a biopsy is performed for involvement of lymphoma cells and monitoring of treatment response. Other investigations include serum protein electrophoresis and identification of paraprotein in certain types of lymphoma. Additional serological tests are often employed for etiological recognition in various types of lymphoma. CT scan of the chest, abdomen and pelvis is employed to stage gastrointestinal lymphomas with a marked sensitivity and specificity. Incorporation of FDG-PET has a significant advantage in staging of DLBCL, follicular lymphoma and MCL with a sensitivity of 80% and a specificity of 90%, although it has no added benefit for MALT lymphomas. EUS has gained momentum as an integral tool in the diagnosis, locoregional staging, and monitoring response of gastrointestinal lymphoma to treatment. EUS is superior to CT scan for the T- and N-staging by providing vivid details for any invasion to the mucosa, submucosa, muscularis propria or beyond serosa. The value of EUS and CT, however, is a matter of debate in the follow-up of patients as it is well established that histological remission precedes the normalization of wall changes in patients with lymphoma[74,75], thus precluding the necessity for endoscopic biopsy follow-up. Gastric MALT lymphoma, though indolent, often warrants a more meticulous staging procedure because it is usually multifocal, transforms to the DLBCL variant, and is difficult to diagnose due to normal endoscopic findings in the majority of cases as well as involvement of multiple organs. Endoscopic biopsies are therefore usually taken from multiple sites of the stomach and duodenum encompassing both normal and abnormal regions[75].

Table 3 Paris staging system for primary gastrointestinal lymphomas.

Stage	Gastrointestinal lymphomas
TX	Lymphoma extent not specified
T0	No evidence of lymphoma
T1	Lymphoma confined to the mucosa/submucosa
T1m	Lymphoma confined to mucosa
T1sm	Lymphoma confined to submucosa
T2	Lymphoma infiltrates muscularis propria or subserosa
T3	Lymphoma penetrates serosa (visceral peritoneum) without invasion of adjacent structures
T4	Lymphoma invades adjacent structures or organs
NX	Involvement of lymph nodes not assessed
N0	No evidence of lymph node involvement
N1	Involvement of regional lymph nodes
N2	Involvement of intra-abdominal lymph nodes beyond the regional area
N3	Spread to extra-abdominal lymph nodes
MX	Dissemination of lymphoma not assessed
M0	No evidence of extranodal dissemination
M1	Non-continuous involvement of separate site in gastrointestinal tract (e.g. stomach and rectum)
M2	Non-continuous involvement of other tissues (e.g. peritoneum, pleura) or organs (e.g. tonsils, parotid gland, ocular, adnexa, lung, liver, spleen, kidney, breast, etc.)
BX	Involvement of bone marrow not assessed
B0	No evidence of bone marrow involvement
B1	Lymphomatous infiltration of bone marrow
TNM	Clinical staging: status of tumor, node, metastasis, bone marrow
pTNMB	Histopathological staging: status of tumor, node metastasis, bone marrow
pN	The histological examination will ordinarily include six or more lymph nodes

The international prognostic index (IPI) developed for DLBCL is, at present, the most valuable and widely used for the stratification of almost all subtypes of NHL (Table 4). However, the IPI does not hold the same predictive value for patients treated with immunochemotherapy. Moreover, the IPI is less useful for follicular lymphoma because a significant number of patients with a poor prognosis are not recognized, thus warranting development of follicular lymphoma IPI[76]. Reevaluation of patients who have completed the whole planned treatment is an integral part in the management of lymphoma patients. The most important prognostic factor for the management is the assessment of complete remission of the disease because salvage treatment with a high dose and autologous or allogenic bone marrow transplantation may be contemplated in those who fail to initial therapy. The different parameters are compared with the prior treatment values and evaluated. A possible necessity of histopathological assessment by follow-up biopsy may be required in certain atypical situations. Nuclear studies and PET in particular have been recommended for the evaluation of recurrence of various lymphomas[77].

Table 4 International prognostic index.

Adverse risk factors

Age > 60 yr

≥ 2 extranodal sites

Ann arbor stage III-IV

Performance status ≥ 2 (ECOG)

High lactate dehydrogenase

Risk

Low (n = 0-1)

Low-intermediate (n = 2)

High-intermediate (n = 3)

High (n = 4-5)

FUTURE PERSPECTIVE

There has been a tremendous leap in the diagnosis, staging and management of gastrointestinal lymphoma in the last two decades. With a better insight into its etiology and molecular aspect, various critical signaling pathways provide an impetus with greater benefits. Identification of the cell surface antigens has led to the introduction of monoclonal antibodies like Rituximab and radioimmunotherapy that can result in a more targeted approach with a significant impact for the overall management of lymphoma. A deep understanding of the role of monoclonal antibodies in the pathogenesis of gastrointestinal lymphoma has led to development of the second and third generations of anti CD-20 antibodies (ofatumumab, veltuzumab, ocrelizumab), anti CD-22 antibodies such a Epratuzumab, anti CD-30 antibodies such as SGN-30, anti CD-40 antibody SGN-40, and anti vascular endothelial growth factor (VEGF) antibody bevacizumab[78]. Furthermore, addition of cytokines and other immune modulators has a boon resulting from a better understanding of the antibody activities at targeted tissues. Agents targeting the Bcl-2, Syk and the PI3K/AKT/mTOR pathways have emerged as a more biologically- focused management with further development in this field[79].

Another important aspect to be considered is the increasing sensitivity and specificity of imaging techniques like EUS and PET-CT in the diagnosis of lymphomas. An emerging field is the molecular imaging with a variety of new radiopharmaceutical agents that target the up-regulated specific receptors in cancer cells[80].

CONCLUSION

The epidemiology, clinical presentation, histopathologic subtypes, as well as radiological presentation of gastrointestinal lymphomas are highlighted in this review, with emphasis laid on the need for accurate diagnosis, staging, treatment of the disease with the promising novel techniques.