Primary squamous cell carcinoma of pancreas diagnosed by EUS-FNA: A case report

Abstract

Squamous cell carcinoma of the pancreas has been sparsely described since the 1940s, and generally has a poor prognosis. Herein, we present a case of primary squamous cell carcinoma of the pancreas with liver metastasis, both confirmed by endoscopic ultrasound-guided fine needle aspiration (EUS-FNA). To the best of our knowledge, this is the first case report in literature utilizing EUS-FNA for a cell-type specific diagnosis of primary pancreatic squamous cell carcinoma with a liver metastasis.

Key Words: Computed tomography, Cytology, Endoscopic ultrasound

INTRODUCTION

Primary squamous cell carcinoma is rare among all pancreatic neoplasms, constituting less than 1% of cases. Herein, we present a case of primary squamous cell carcinoma of the pancreas with liver metastasis, both confirmed by endoscopic ultrasound-guided fine needle aspiration (EUS-FNA).

CASE REPORT

A 76-year-old American African female was referred with a few weeks history of dull epigastric pain with radiation to the back, and weight loss of 10 pounds. Initial physical examination revealed only minimal tenderness over the epigastrium, and blood tests were all normal including serum lipase (29 IU/L, reference: 10-50 IU/L) and CA 19-9 (2 IU/mL, reference: 0-37 IU/mL). Upper endoscopy showed mild gastritis. Subsequent computed tomography (CT) of the thorax and abdomen revealed a 5 cm partial cystic mass in the tail of the pancreas and a 1 cm subtle hypodense non-enhanced lesion in the left lobe of the liver, with normal chest and mediastinum. CT-guided biopsy of the liver mass was performed, however, preliminary histology only revealed atypical cells. Endoscopic ultrasound (EUS) was performed for clarification of the pathology. A complex cystic mass with a large solid component was seen in the tail of the pancreas measuring up to 68 mm. Another 14 mm × 18 mm ill-defined, almost isoechoic lesion was also noted in the left lobe of the liver (Figure 1). Transgastric EUS-FNA, using a 25-gauge needle, of both the liver and tail of pancreas lesions was carried out, which revealed squamous cell carcinoma in both sites, although on-site interpretation was difficult due to the unusual cell type (Figure 2).

Figure 1 Endoscopic ultrasound image of the heterogenous, nearly isoechoic lesion in the left lobe of the liver (A) and the complex cystic mass in the tail of pancreas (B).

Figure 2 Fine-needle aspiration specimen. A: Liver mass (HE, × 100); B: Pancreatic mass (HE, × 100). The cell block shows atypical squamous cells consistent with keratinizing squamous cell carcinoma. C: Liver mass (ThinPrep, × 400). Squamous cell contamination from the esophagus as evidenced by the presence of bacteria and fungal organisms.

DISCUSSION

Squamous cell carcinoma of the pancreas has been rarely described since the 1940s, and generally has a poor prognosis[1]. It is hypothesized that squamous metaplasia of pancreatic ductal epithelium after chronic inflammation (e.g. chronic pancreatitis), could be one of the possible oncogenic mechanisms[2]. A subset of pancreatic adenocarcinoma, adenosquamous carcinoma is occasionally found in surgical specimens after Whipple’s operation. In one series, dual differentiation towards both adenocarcinoma and squamous cell carcinoma was seen in 25 pancreatic cancer patients[3]. However, pure squamous cell carcinoma of the pancreas is extremely rare, and is often mistaken as either benign squamous cells from upper gastrointestinal contamination when it is well-differentiated, or metastasis from other sites (e.g. lung and upper aerodigestive tract) when it is obviously malignant. A MEDLINE search only identified 14 case reports in the English literature so far[4-17], and all diagnoses were based on surgical specimens. Hypervascularity on contrast CT has been reported as a characteristic finding, but was not seen in this case[15].

Since the introduction of EUS-FNA for investigating pancreatic cancer in the 1990s[18], it has now become the standard procedure for pancreatic lesions. Cytopathological confirmation can be obtained with EUS-FNA, so as to avoid unnecessary pancreatic resection[19]. From our knowledge, this is the first case report in the literature utilizing EUS-FNA for a cell-type specific diagnosis of primary pancreatic squamous cell carcinoma with a liver metastasis. The distinction of well-differentiated squamous cell carcinoma from benign disease such as lymphoepithelial cysts (LEC) of the pancreas may be difficult. LEC is an infrequent benign condition and EUS-FNA typically shows squamous cells, lymphocytes, notched crystals and keratin debris[20-22]. Because cystic degeneration can occur in pancreatic cancers, as in our case[23], differentiation between benign and malignant squamous cell lesions could be difficult. If there is a solid component, it should be targeted during EUS-FNA rather than the cyst. In general, dense orangeophilic keratin debris, atypical parakeratosis, and nuclear atypia including hyperchromasia and nuclear membrane irregularities help us to differentiate cancer from reactive squamous metaplastic cells[24]. A glandular component should also be sought when noting atypical squamous carcinoma cells, as adenosquamous carcinoma is more common than the pure squamous cell type[3]. Squamous cell contaminants could also contribute to diagnostic uncertainty; although transgastric and transduodenal routes for EUS-FNA should not produce many of these cells, however, they appear to have been noted in our case (Figure 2C)[25]. In this patient, diagnosis of primary squamous cell carcinoma of the pancreas with liver metastasis was confirmed, as EUS-FNA obtained the same type of cancer cells from both pancreatic and liver lesions, and CT and upper endoscopy did not identify other possible primary squamous cell malignancy.