Intraductal oncocytic papillary neoplasm having clinical characteristics of mucinous cystic neoplasm and a benign histology.

CONTEXT An intraductal oncocytic papillary neoplasm is a rare pancreatic tumor which was first described by Adsay et al. in 1996. It has been defined as a new subgroup of IPMN. CASE REPORT We report the case of a 76-year-old woman who presented with nausea. Imaging studies revealed a cystic mass in the body of the pancreas. She underwent a successful distal pancreatectomy and splenectomy, and has subsequently remained well. Microscopically, the cyst was lined by columnar epithelium similar to pancreatic duct epithelium, and the nodular projection consisted of arborizing papillary structures, lined by plump cells with abundant eosinophilic cytoplasm. These eosinophilic cells were immunohistochemically positively stained with anti-mitochondrial antibody. The cellular atypism was mild and the proliferating index was low, compatible with adenoma of an intraductal oncocytic papillary neoplasm. Although no ovarian type stroma was identified, in our case, no communication to main pancreatic duct (located in the pancreatic body) and rapid growth by intracystic hemorrhage were clinical characteristics of a mucinous cystic neoplasm, but not IPMN. CONCLUSION With only 17 cases reported to date, the clinical and pathological details of an intraductal oncocytic papillary neoplasm are still unclear. We herein add one case with different characteristics from those of the past reports. To our knowledge, this is the first case report of an intraductal oncocytic papillary neoplasm with the clinical characteristics of a mucinous cystic neoplasm.