Pancreatic mucinous cystic neoplasm of the main pancreatic duct.

Mucinous cystic neoplasm and intraductal papillary mucinous neoplasm are 2 types of cystic pancreatic mucinous tumors, each with its own distinct clinicopathologic features and pathogenetic mechanisms. We report here an unusual pancreatic mucinous neoplasm with features of both a mucinous cystic neoplasm and an intraductal papillary mucinous neoplasm in a 40-year-old woman who underwent total pancreatectomy. The endoscopic retrograde cholangiopancreatogram and gross examination demonstrated a mucin-producing intraductal neoplasm involving the length of the main pancreatic duct, typical of main duct intraductal papillary mucinous neoplasm, but histology of the main duct showed involvement by a biphasic tumor composed of columnar epithelium overlying ovarian-type stroma, characteristic of a mucinous cystic neoplasm. Immunohistochemistry confirmed that the stromal cells expressed estrogen and progesterone receptors, inhibin, and calretinin. Pancreatic mucinous cystic neoplasm involving the entire main pancreatic duct has not, to our knowledge, been previously reported.