Lymphoepithelial cyst of the pancreas.

Cystic lesions of the pancreas can be divided into true cysts, pseudocysts, and cystic neoplasms. Lymphoepithelial cysts (LECs) are a type of true cyst that can mimic pseudocysts and cystic neoplasms. LECs are rare lesions; fewer than 90 cases have been reported in the English language literature. The case of a 60-year-old man with an LEC of the pancreas is reported. He was admitted with upper abdominal discomfort. Computed tomography showed a 64 × 39 mm cystic mass in the retroperitoneum behind the duodenum and inferior caval vein. Magnetic resonance imaging revealed a right-sided mass on T1-weighted imaging, with a clear boundary between the mass and its surroundings, except for the pancreas. The mass had an inhomogeneous intensity on T2-weighted imaging. Within the mass, small floating nodules with low intensity were seen. Endoscopic ultrasound showed many high-echoic nodules and smaller grains scattered everywhere in the mass. Fine needle aspiration and cytologic examination were performed. Characteristic chylaceous fluid was obtained in which anucleate squamous cells were found. There were also a few atypical large cells with irregularly shaped marked nucleoli and degenerative cytoplasm. Cytologic diagnosis was suspicious for malignancy. The lesion was diagnosed as a retroperitoneal cyst, probably of pancreatic origin. Since a neoplastic lesion could not be ruled out, surgery was performed. The lesion was palpable on the dorsal side of the second portion of the duodenum. The mass was completely resected. Macroscopically, the lesion was a multilocular cyst with a thin septal wall. The cyst was filled with cottage cheese-like substance. Microscopically, the cyst wall was composed of stratified squamous epithelium and dense subepithelial lymphatic tissue with developed lymph follicles. The epithelial cells had no atypia. The histopathologic diagnosis was LEC of the pancreas. The patient's postoperative course was good.