Squamoid cystosis of pancreatic ducts: a variant of a newly-described cystic lesion, with evidence for an obstructive etiology

Abstract

We describe a 40-year-old man who was found to have a cystic mass in the pancreatic tail during workup for weight loss and abdominal discomfort. Although computed tomography scan showed a single cyst associated with dilatation of the main pancreatic duct, gross and histologic examination of the distal pancreatectomy specimen actually revealed a central cyst that was surrounded by multiple smaller cystic spaces. This distinctive appearance was formed from extensive cystic dilatation and squamous metaplasia of the native pancreatic duct system. Further, a traumatic neuroma was discovered near the junction between normal and abnormal parenchyma. We believe that this case represents a variant of the newly-described squamoid cyst of pancreatic ducts which we term squamoid cystosis of pancreatic ducts. The presence of chronic pancreatitis and a traumatic neuroma supports the hypothesis that squamoid cysts are non-neoplastic lesions arising from prior duct obstruction.

Keywords: benign; pancreas; tumors.

Figure 1.

A) Computed tomography scan of the abdomen shows a cyst in the tail of the pancreas (arrowhead), which appears connected to the dilated main pancreatic duct (arrow). B) Gross photograph of the pancreatic tail reveals a 2.5 cm unilocular cyst adjacent to the dialted main pancreatic duct (asterisk). The surrounding parenchyma is fibrotic and contains multiple smaller cystic spaces (arrowheads); near the resection margin at right, the pancreatic parenchyma assumes a more normal gross appearance.

Figure 2.

A) Cluster of cystically-dilated pancreatic ducts. The intervening parenchyma shows chronic pancreatitis with mild lymphocytic inflammation, scattered islets, and near-total loss of acini (Hematoxylin and Eosin, ×20). B) Nodules of squamous metaplasia surrounding the smallest pancreatic ducts; focally the luminal epithelium is cuboidal (arrow) (Hematoxylin and Eosin, ×100). Immunostaining for p63 (inset, 100) highlights the squamoid epithelium but spares the overlying ductal epithelial cells in these small ducts.

Figure 3.

Granular cell traumatic neuroma, which shows infiltration around small pancreatic ducts with squamous metaplasia (upper right); normal acinar parenchyma can be seen in the lower left corner (Hematoxylin and Eosin, ×20). Lesional cells are intensely S100+ (inset, ×100).