Mucinous cystic neoplasm in a young male patient.

A 25-year-old Japanese man was admitted to our hospital with a history of recurrent pancreatitis and a pseudocyst of the pancreas. Abdominal computed tomography (CT) and magnetic resonance imaging (MRI) revealed an encapsulated multilocular cystic mass 5 cm in diameter in the pancreatic tail. Endoscopic ultrasonography demonstrated a mural nodule, and endoscopic retrograde pancreatography showed a communication of the lesion with the main pancreatic duct. A neoplastic cystic tumor was suspected, and a resection of the body tail of the pancreas was performed. The lesion was a multilocular cyst having a common fibrous capsule and viscous content. Histologically, the cystic lesion was lined with a single layer of columnar cells with low-grade atypia. Ovarian-type stroma (OS) was confirmed, and it showed positive for antiestrogen receptor and antiprogesteron receptor staining. Based on these findings, the lesion was diagnosed as mucinous cystic neoplasm (MCN), an adenoma that shows extraordinarily high prevalence in women. Further study on the pathogenesis of MCN in male patients should be undertaken to elucidate the process of development.