Squamoid cyst of pancreatic ducts: a challenging differential diagnosis among benign pancreatic cysts

Squamoid cyst of pancreatic ducts: A case report

The term squamoid cyst of pancreatic ducts (SCOP) has been proposed recently, and it is a very rare benign lesion. We report a case of SCOP in a patient who underwent laparoscopic distal pancreatectomy. A 51-year-old woman presented with a pancreatic cystic lesion (3.3 cm) as an incidental finding on abdominal ultrasonography. A computed tomography scan showed a well-defined cystic lesion in the body of the pancreas with peripheral nodular calcification. Histology showed a unilocular cyst with a thin, fibrotic wall, and it was surrounded by normal-appearing pancreatic tissue. The lining of the cyst was composed of stratified non-keratinized squamous epithelium without significant nuclear atypia. Immunohistochemistry showed positive nuclear p63 expression in the cyst lining. The final diagnosis of SCOP was established. It is important to distinguish SCOPs from mucinous pancreatic cysts that have malignant potential. Preoperative diagnosis of SCOP is still difficult, and further studies are needed to identify specific preoperative characteristics that can accurately distinguish this lesion.

Intraductal papillary squamous neoplasm of the pancreas: Cyto-histologic correlation of a novel entity

We correlate the cytologic and histologic features of a squamous-lined pancreatic cystic lesion with a complex papillary architecture and an associated KRAS mutation, which to our knowledge has not been previously described. A 69 year-old woman presented with intermittent left upper quadrant pain. CT imaging revealed a 1 cm solid lesion in the pancreatic tail with peripheral calcification. Endoscopic ultrasound-guided fine needle biopsy showed a proliferation of epithelial cells with fibrovascular cores. An immunohistochemical stain for p40 was positive in the lesional cells. A distal pancreatectomy revealed a unilocular, cystic, well-circumscribed, soft and friable mass measuring 1.0 × 1.0 × 0.8 cm. Histologically, the cyst was lined by nonkeratinizing stratified squamous epithelium with a complex papillary architecture, filling the cyst lumen. Molecular sequencing revealed a KRAS G12V missense mutation. While the lesion shared some histologic features with the previously described "squamoid cyst of the pancreatic ducts", the complex papillary architecture and presence of a KRAS mutation are unique to the entity we describe herein and we propose the name "intraductal papillary squamous neoplasm of the pancreas." Reporting the cytomorphologic features of this novel entity may help in identification of similar lesions and understanding of the clinicopathologic significance.

Benign Tumors and Tumorlike Lesions of the Pancreas

The pancreas is a complex organ that may give rise to large number of neoplasms and non-neoplastic lesions. This article focuses on benign neoplasms, such as serous neoplasms, and tumorlike (pseudotumoral) lesions that may be mistaken for neoplasm not only by clinicians and radiologists, but also by pathologists. The family of pancreatic pseudotumors, by a loosely defined conception of that term, includes a variety of lesions including heterotopia, hamartoma, and lipomatous pseudohypertrophy. Autoimmune pancreatitis and paraduodenal ("groove") pancreatitis may also lead to pseudotumor formation. Knowledge of these entities will help in making an accurate diagnosis.

Pancreatic hamartoma: a case report and literature review

Background

Pancreatic hamartoma is an extremely rare benign disease of the pancreas. Only 30 cases have been reported to date.

Case presentation

A 68-year-old man presented with an asymptomatic solid and multi-cystic lesion in the uncus of the pancreas, incidentally detected on abdominal enhanced computed tomography. The tumor was found to be a well-demarcated solid and multi-cystic lesion without any enhancement, measuring 4 cm in diameter. After 28 months of follow-up, the tumor enlarged. At 31 months after initial diagnosis, the patient underwent surgical resection because it was difficult to clinically determine whether the tumor was malignant or not. Macroscopically, the solid tumor consisted of yellow adipose tissue with a smooth thin capsule confined to the pancreatic uncus. The inner structure of the tumor consisted of multiple cysts with a white nodule between the cysts. Histologically, the solid part and the multi-cystic portion consisted of mature adipose tissue and colonization of dilated pancreatic ducts with mild fibrosis, respectively. Immunohistochemical findings revealed cytokeratin 7 and 19 positive staining in the epithelial cells of the ducts. Adipose tissue showed positive staining for S-100 protein and there were only a few MIB-1 positive cells. The tumor was then diagnosed as a pancreatic hamartoma.

Conclusion

Beside on the above findings, we suggest that the term “well-demarcated solid and cystic lesion with chronological morphological changes” could be a clinical keyword to describe pancreatic hamartomas.

Electronic supplementary material

The online version of this article (doi:10.1186/s12876-016-0419-2) contains supplementary material, which is available to authorized users.