Published online Apr 15, 2010. doi: 10.4251/wjgo.v2.i4.192
Revised: February 6, 2010
Accepted: February 13, 2010
Published online: April 15, 2010
New insights emerged last decade that enriched our knowledge regarding the biological behavior of appendiceal neuroendocrine tumors (NETs), which range from totally benign tumors less than 1cm to goblet cell carcinomas which behave similarly to colorectal adenocarcinoma. The clinical implication of that knowledge reflected to surgical strategies which also vary from simple appendicectomy to radical abdominal procedures based on specific clinical and histological characteristics. Since the diagnosis is usually established post-appendicectomy, current recommendations focus on the early detection of: (1) the subgroup of patients who require further therapy; (2) the recurrence based on the chromogranin a plasma levels; and (3) other malignancies which are commonly developed in patients with appendiceal NETs.
- Citation: Griniatsos J, Michail O. Appendiceal neuroendocrine tumors: Recent insights and clinical implications. World J Gastrointest Oncol 2010; 2(4): 192-196
- URL: https://www.wjgnet.com/1948-5204/full/v2/i4/192.htm
- DOI: https://dx.doi.org/10.4251/wjgo.v2.i4.192
In 1907, Oberndorfer first introduced the term “carcinoid” to describe “little carcinomas” of the small intestine which were thought (by him at that time) to be probably benign.
However, the continuous knowledge which was added by studying these tumors for nearly a century strengthen the notion that the above term was inaccurate or inadequate to describe several parameters of this heterogeneous group of gastrointestinal tumors (including the appendiceal one). Thus, the term “carcinoid” was replaced by the term “gastroenteropancreatic neuroendocrine tumors, GEP-NETs”. The term “appendiceal NET” will be used hereafter.
According to the current WHO classification, appendiceal NETs are classified as: (1a) Well differentiated NETs with benign biological behaviour or (1b) Well differentiated NETs with uncertain malignant potential; (2) Well differentiated neuroendocrine carcinoma (with low malignant potential); and (3) Mixed exocrine-neuroendocrine carcinoma. Goblet cell carcinoma (synonyms: adenocarcinoid, mucous adenocarcinoid) belongs to the last category.
Although appendiceal NETs constitute an unusual and sporadic entity, it accounts for more than 50% of all primary tumors of the appendix.
Benign appendiceal NETs represent the second commonest neuroendocrine neoplasms of the gastrointestinal tract (small bowel NETs being the commonest) and their histological diagnosis is established, usually incidentally, in 0.3%-0.9% of patients undergoing appendicectomy. This means that the probability of a surgeon coming across an appendiceal NET is once for every 100 to 300 appendectomies performed by him. The annual incidence is about 2-3 newly diagnosed cases per million of general population although post-mortem studies increase the incidence to 170 cases per 100000. The mean age of patients at the time of diagnosis is at end of the second decade of life with an increased incidence among females[5-8]. The last finding probably reflects the increased use of diagnostic laparoscopy among females for atypical lower abdominal pain and the concomitant laparoscopic appendectomies performed.
Malignant appendiceal NETs represent the third commonest (after small bowel and rectum) malignant neuroendocrine neoplasms of the gastrointestinal tract with an annual incidence of 0.63 cases per million of the general population and the mean age of the patients at time of the diagnosis in the 5th decade of life.
Normally, appendiceal NETs remain asymptomatic. Although accurate preoperative diagnosis using abdominal computed tomography (CT) or ultrasound scans has been reported, the total number of the enrolled patients is extremely small (only case reports have been published) and thus is not suitable for definite conclusions. Therefore, for the vast majority of cases, the diagnosis of appendiceal NETs is established incidentally postoperatively in the specimens of appendectomies which had been performed due to either acute appendicitis or recurrent, chronic, dull, non-specific lower right quadrant abdominal pain[6,12]. Carcinoid syndrome is very uncommon (< 1%).
Since most appendiceal NETs are diagnosed postoperatively, any effort to be diagnosed preoperatively is practically unrealistic so the diagnostic work-up should focus on the early detection of recurrence in patients who have already had surgery.
The use of plasma chromogranin-A levels as a tumor marker contributes to the differential diagnosis from goblet cell carcinoma, the early detection of recurrence and the long term follow-up of metastatic disease. All patients should be investigated 6 and 12 mo postoperatively and then annually while the follow-up should be lifelong.
Especially for tumors > 2 cm, a CT scan and somatostatin receptor scintigraphy (SRS) is recommended at 6 mo and 12 mo postoperatively and then annually. Colonoscopy is advised for the early detection of synchronously present or metachronously developed large bowel tumors.
Approximately 80% of appendiceal NETs have a maximum diameter of < 1 cm, 15% have a diameter 1-2 cm and only 5% have a diameter greater than 2 cm. Tumor size greater than 2 cm strongly correlates both to metastatic potential and to an unfavourable 5 years survival rate.
Approximately 70%-75% of the tumors are located in the apex, 15%-20% in the body and 5%-10% in the base of the organ. Although there is not enough evidence to support the theory that the location of the tumor correlates to the overall survival, cecum invasion or positive resection margins should be considered for planned future therapeutic strategies.
A multifocal pattern of the disease along the appendix has not been described yet. However, the coexistence of appendiceal NET with small bowel or rectal NETs, colorectal cancer, Crohn’s disease and synchronous or metachronous development of malignancies outside the gastrointestinal tract are well documented.
The possibility of lymph node metastases from appendiceal NETs with vascular invasion is estimated as high as 30% but only 1% for tumors with appendiceal mesentery invasion. However, the prognostic significance of appendiceal mesentery invasion remains controversial since its relationship to distant metastases development has been reported as between 0 and 4.1%. To date, there have been no reports correlating lymph node metastases to appendiceal serosa invasion.
The rate of cellular proliferation (as it expressed by the Ki-67) does not seem to be of prognostic value.
Based on the analysis of the published report from the SEER database between 1977-2004, it is suggested that the first proposed TNM classification and staging systems for appendiceal NETs (which was based on the report from the SEER database between 1973-1999) should be modified according to Table 1.
|IV||Any Τ||Any Ν||Μ1|
Current guidelines[13,22,23] propose simple appendectomy as adequate and curative for the treatment of appendiceal NETs < 1 cm, while for tumors 1-2 cm, a simple appendectomy followed by periodic postoperative follow-up for 5 years is recommended.
Right hemicolectomy (within 3 mo from the appendicectomy) should be reserved for patients in whom at least one of the following criteria is present: tumor size > 2 cm, location of the tumor at the base of the appendix, infiltration of the cecum, positive surgical resection margins, appendiceal mesentery invasion, metastatically infiltrated mesoappendiceal lymph node, presence of undifferentiated or low differentiated cells or presence of goblet cells.
Serosal, vascular, lymphatic or perineural invasion alone does not constitute inclusion criteria for right hemicolectomy.
Goblet cell carcinomas (GCC) constitute less than 5% of all primary appendiceal tumors and, similar to the appendiceal NETs, their diagnosis is established usually incidentally in 0.3%-0.9% of patients undergoing appendicectomy. Its annual incidence is 0.05 new cases per 100000 of general population with an equal distribution between the sexes and the mean age of the patients at the time of diagnosis in the 6th decade of life, nearly 20 years later than the mean age of the diagnosis of malignant appendiceal NETs and almost 10 years earlier than the mean age of the diagnosis of the appendiceal adenocarcinoma.
GCC is derived from undifferentiated stem cells which are completely different from the endocrine cells in the mucosal stroma. The degree of integration of the goblet cells versus APUD cells varies from pure GCC to pure carcinoid tumor. GCC cells have two type of granules which are mainly acid mucinous, are not mixed and can be recognized by different histochemical staining.
In their recent study, Tang et al tried to answer the long-standing question: “Should GCCs be classified as NETs or as de novo mucous adenocarcinomas of the appendix?” Based on histological findings, they proposed classification of GCCs in: (1) Typical GCC (type A); (2) adenocarcinoma ex GCC, signet ring cell type (Type B); and (3) adenocarcinoma ex GCC, poorly differentiated carcinoma type (Type C).
On one hand, GCCs are developed in epithelium without dysplasia and this development is not related to the adenoma-carcinoma sequence of carcinogenesis. The immuno-phenotype of typical GCCs is different from the immuno-phenotype of adenocarcinoma and genetic alterations of neuroendocrine origin, completely different from the genetic alterations which lead to adenocarcinoma formation, are responsible for that. Moreover, both NETs and GCCs of the appendix express chromogranin-A.
On the other hand, the positive expression of p53 range from 0% in type A GCC to 100% in type C GCC, findings suggestive that for the transformation to the adenocarcinoma phenotype in type C, the immunohistochemical expression of Cytokeratins (CK) 7 and 20 in appendiceal NETs and GCCs disclosed that GCCs express CKs similarly to colonic adenocarcinomas, while NETs do not. Immunohistochemical expression of Math1 and HD5 is observed in GCCs but not in NETs while the biological behavior of GCCs is identical to adenocarcinomas but not to NETs.
Based on the above findings, it is proposed that GCCs should constitute a distinct histological and clinical entity different from the appendiceal NETs, while the classification which is proposed by Wang et al seems to comply to the biological behavior of the tumors and with the prognosis of the patients.
In the majority of cases, the disease remains asymptomatic. Acute appendicitis (due to luminal obstruction by the tumor) is the main symptom followed by atypical abdominal pain and abdominal mass. Unusual symptoms are intussusception, gastrointestinal bleeding, bowel obstruction, anemia and miscellaneous urinary manifestations.
In 11% of cases the disease is already metastatic at the time of diagnosis, mainly to the ovaries and peritoneum. However, studies propose that the ovarian metastases should be considered as secondary to adenocarcinoma rather than to appendiceal GCC, further supporting the proposed by Tang et al classification.
In fact, most appendiceal GCCs are diagnosed postoperatively so any effort for accurate preoperative diagnosis is unrealistic. The diagnostic work-up should focus on the early detection of recurrence in patients who have already had surgery.
Magnetic resonance imaging is more sensitive than CT and CT more sensitive than SRS in the early detection of pulmonary, hepatic and peritoneal metastases. Plasma chromogranin-A levels have no diagnostic value while the periodic measurement of tumor markers related to the mucinous characteristics of the tumor such as CEA, CA 19-9 and CA 125 is recommended. Lifelong screening for synchronous or metachronous malignancies is also recommended.
Right hemicolectomy (usually performed after the initial appendectomy) is recommended as the treatment of choice after the histological confirmation of GCC independent of the size of the primary tumor. In female patients with GCC of the appendix, regardless of age, bilateral salpingo-oophorectomy is also advocated. In cases with advanced peritoneal dissemination, cytoreductive surgery with adjuvant intraperitoneal chemotherapy may offer prolonged survival. Adjuvant chemotherapy is usually not effective although it can be used in patients with obvious spread of the disease. Chemotherapeutic protocols are the same as those used in the treatment of colorectal adenocarcinoma.
Based on new insights that emerged last decade, the biological behavior of appendiceal NETs ranges from totally benign tumors less than 1 cm to goblet cell carcinomas which behave similarly to colorectal adenocarcinoma. Depending on specific clinical and histological characteristics, surgical strategies also vary from simple appendicectomy to radical abdominal procedures (Table 2). Since, in the vast majority of cases, the diagnosis is usually established post-appendicectomy, it is crucial for clinicians to identify the subgroup of patients who require further therapy, to detect early the recurrence based on the chromogranin A plasma levels and to detect early other malignancies which are commonly developed in patients with appendiceal NETs.
|Indications||Type of operation|
|Tumor size < 1 cm||Appendicectomy|
|Tumor size 1-2 cm||Appendicectomy + Regular F/Up for 5 years|
|Tumor size > 2 cm||Right hemicolectomy|
|Location of the tumor at the base of the appendix||Right hemicolectomy|
|Infiltration of the cecum||Right hemicolectomy|
|Positive surgical resection margins||Right hemicolectomy|
|Appendiceal mesentery invasion||Right hemicolectomy|
|Metastatically infiltrated mesoappendiceal lymph node||Right hemicolectomy|
|Presence of undifferentiated or low differentiated cells||Right hemicolectomy|
|Presence of goblet cells|
|Goblet cell carcinoma in males||Right hemicolectomy|
|Goblet cell carcinoma in females (regardless of age)||Right hemicolectomy + Bilateral salpingo-oophorectomy|
|Peritoneal dissemination from goblet cell carcinoma||Cytoreductive surgery + Adjuvant intraperitoneal chemotherapy|
Peer reviewer: Ondrej Slaby, PhD, Department of Comprehensive Cancer Care, Masaryk Memorial Cancer Insitute, Zluty kopec 7, 656 53 Brno, Czech
S- Editor Li LF L- Editor Roemmele A E- Editor Yang C
|1.||Modlin IM, Shapiro MD, Kidd M. Siegfried Oberndorfer: origins and perspectives of carcinoid tumors. Hum Pathol. 2004;35:1440-1451. [Cited in This Article: ]|
|2.||Chetty R. Requiem for the term 'carcinoid tumour' in the gastrointestinal tract? Can J Gastroenterol. 2008;22:357-358. [Cited in This Article: ]|
|3.||Klöppel G, Perren A, Heitz PU. The gastroenteropancreatic neuroendocrine cell system and its tumors: the WHO classification. Ann N Y Acad Sci. 2004;1014:13-27. [Cited in This Article: ]|
|4.||Connor SJ, Hanna GB, Frizelle FA. Appendiceal tumors: retrospective clinicopathologic analysis of appendiceal tumors from 7,970 appendectomies. Dis Colon Rectum. 1998;41:75-80. [Cited in This Article: ]|
|5.||Goede AC, Caplin ME, Winslet MC. Carcinoid tumour of the appendix. Br J Surg. 2003;90:1317-1322. [Cited in This Article: ]|
|6.||Modlin IM, Lye KD, Kidd M. A 5-decade analysis of 13,715 carcinoid tumors. Cancer. 2003;97:934-959. [Cited in This Article: ]|
|7.||Stinner B, Rothmund M. Neuroendocrine tumours (carcinoids) of the appendix. Best Pract Res Clin Gastroenterol. 2005;19:729-738. [Cited in This Article: ]|
|8.||Maggard MA, O'Connell JB, Ko CY. Updated population-based review of carcinoid tumors. Ann Surg. 2004;240:117-122. [Cited in This Article: ]|
|9.||Newton JN, Swerdlow AJ, dos Santos Silva IM, Vessey MP, Grahame-Smith DG, Primatesta P, Reynolds DJ. The epidemiology of carcinoid tumours in England and Scotland. Br J Cancer. 1994;70:939-942. [Cited in This Article: ]|
|10.||Pickhardt PJ, Levy AD, Rohrmann CA Jr, Kende AI. Primary neoplasms of the appendix: radiologic spectrum of disease with pathologic correlation. Radiographics. 2003;23:645-662. [Cited in This Article: ]|
|11.||Deeg KH, Reisig A, Seitz G. Sonographic diagnosis of a carcinoid tumour of the appendix in a 14-year-old boy. Ultraschall Med. 2003;24:120-122. [Cited in This Article: ]|
|12.||O'Donnell ME, Carson J, Garstin WI. Surgical treatment of malignant carcinoid tumours of the appendix. Int J Clin Pract. 2007;61:431-437. [Cited in This Article: ]|
|13.||Plöckinger U, Couvelard A, Falconi M, Sundin A, Salazar R, Christ E, de Herder WW, Gross D, Knapp WH, Knigge UP. Consensus guidelines for the management of patients with digestive neuroendocrine tumours: well-differentiated tumour/carcinoma of the appendix and goblet cell carcinoma. Neuroendocrinology. 2008;87:20-30. [Cited in This Article: ]|
|14.||Debnath D, Rees J, Myint F. Are we missing diagnostic opportunities in cases of carcinoid tumours of the appendix? Surgeon. 2008;6:266-272. [Cited in This Article: ]|
|15.||Moertel CG, Weiland LH, Nagorney DM, Dockerty MB. Carcinoid tumor of the appendix: treatment and prognosis. N Engl J Med. 1987;317:1699-1701. [Cited in This Article: ]|
|16.||McGory ML, Maggard MA, Kang H, O'Connell JB, Ko CY. Malignancies of the appendix: beyond case series reports. Dis Colon Rectum. 2005;48:2264-2271. [Cited in This Article: ]|
|17.||Safioleas MC, Moulakakis KG, Kontzoglou K, Stamoulis J, Nikou GC, Toubanakis C, Lygidakis NJ. Carcinoid tumors of the appendix. Prognostic factors and evaluation of indications for right hemicolectomy. Hepatogastroenterology. 2005;52:123-127. [Cited in This Article: ]|
|18.||Khan MN, Moran BJ. Four percent of patients undergoing colorectal cancer surgery may have synchronous appendiceal neoplasia. Dis Colon Rectum. 2007;50:1856-1859. [Cited in This Article: ]|
|19.||Freeman HJ. Appendiceal carcinoids in Crohn's disease. Can J Gastroenterol. 2003;17:43-46. [Cited in This Article: ]|
|20.||Rossi G, Valli R, Bertolini F, Sighinolfi P, Losi L, Cavazza A, Rivasi F, Luppi G. Does mesoappendix infiltration predict a worse prognosis in incidental neuroendocrine tumors of the appendix? A clinicopathologic and immunohistochemical study of 15 cases. Am J Clin Pathol. 2003;120:706-711. [Cited in This Article: ]|
|21.||Rindi G, Klöppel G, Couvelard A, Komminoth P, Körner M, Lopes JM, McNicol AM, Nilsson O, Perren A, Scarpa A. TNM staging of midgut and hindgut (neuro) endocrine tumors: a consensus proposal including a grading system. Virchows Arch. 2007;451:757-762. [Cited in This Article: ]|
|22.||Landry CS, Woodall C, Scoggins CR, McMasters KM, Martin RC 2nd. Analysis of 900 appendiceal carcinoid tumors for a proposed predictive staging system. Arch Surg. 2008;143:664-670; discussion 670. [Cited in This Article: ]|
|23.||Ramage JK, Davies AH, Ardill J, Bax N, Caplin M, Grossman A, Hawkins R, McNicol AM, Reed N, Sutton R. Guidelines for the management of gastroenteropancreatic neuroendocrine (including carcinoid) tumours. Gut. 2005;54 Suppl 4:iv1-iv16. [Cited in This Article: ]|
|24.||Hemminki K, Li X. Incidence trends and risk factors of carcinoid tumors: a nationwide epidemiologic study from Sweden. Cancer. 2001;92:2204-2210. [Cited in This Article: ]|
|25.||Aizawa M, Watanabe O, Naritaka Y, Katsube T, Imamura H, Kinoshita J, Shimakawa T, Kobayashi S, Asaka S, Haga S. Adenocarcinoid of the appendix: report of two cases. Surg Today. 2003;33:375-378. [Cited in This Article: ]|
|26.||Pahlavan PS, Kanthan R. Goblet cell carcinoid of the appendix. World J Surg Oncol. 2005;3:36. [Cited in This Article: ]|
|27.||Tang LH, Shia J, Soslow RA, Dhall D, Wong WD, O'Reilly E, Qin J, Paty P, Weiser MR, Guillem J. Pathologic classification and clinical behavior of the spectrum of goblet cell carcinoid tumors of the appendix. Am J Surg Pathol. 2008;32:1429-1443. [Cited in This Article: ]|
|28.||Stancu M, Wu TT, Wallace C, Houlihan PS, Hamilton SR, Rashid A. Genetic alterations in goblet cell carcinoids of the vermiform appendix and comparison with gastrointestinal carcinoid tumors. Mod Pathol. 2003;16:1189-1198. [Cited in This Article: ]|
|29.||Modlin IM, Kidd M, Latich I, Zikusoka MN, Eick GN, Mane SM, Camp RL. Genetic differentiation of appendiceal tumor malignancy: a guide for the perplexed. Ann Surg. 2006;244:52-60. [Cited in This Article: ]|
|30.||Alsaad KO, Serra S, Schmitt A, Perren A, Chetty R. Cytokeratins 7 and 20 immunoexpression profile in goblet cell and classical carcinoids of appendix. Endocr Pathol. 2007;18:16-22. [Cited in This Article: ]|
|31.||van Eeden S, Offerhaus GJ, Hart AA, Boerrigter L, Nederlof PM, Porter E, van Velthuysen ML. Goblet cell carcinoid of the appendix: a specific type of carcinoma. Histopathology. 2007;51:763-773. [Cited in This Article: ]|
|32.||Wang HL, Dhall D. Goblet or signet ring cells: that is the question. Adv Anat Pathol. 2009;16:247-254. [Cited in This Article: ]|
|33.||Hristov AC, Young RH, Vang R, Yemelyanova AV, Seidman JD, Ronnett BM. Ovarian metastases of appendiceal tumors with goblet cell carcinoidlike and signet ring cell patterns: a report of 30 cases. Am J Surg Pathol. 2007;31:1502-1511. [Cited in This Article: ]|
|34.||Dromain C, de Baere T, Lumbroso J, Caillet H, Laplanche A, Boige V, Ducreux M, Duvillard P, Elias D, Schlumberger M. Detection of liver metastases from endocrine tumors: a prospective comparison of somatostatin receptor scintigraphy, computed tomography, and magnetic resonance imaging. J Clin Oncol. 2005;23:70-78. [Cited in This Article: ]|
|35.||Mahteme H, Sugarbaker PH. Treatment of peritoneal carcinomatosis from adenocarcinoid of appendiceal origin. Br J Surg. 2004;91:1168-1173. [Cited in This Article: ]|