Mucinous cystadenoma of the pancreas with huge mural hematoma

A 60-year-old woman was referred for evaluation of a cystic mass in the pancreatic body that extended to the tail. Transabdominal ultrasonography demonstrated an oval cystic mass 24 cm in diameter, filled with debris. On the cyst wall there was a wide-based, smooth-surfaced, heterogeneous high-echoic protrusion that was 5 cm in diameter. On CT the protrusion showed internal enhancement. Endoscopic pancreatography showed no intraductal mucin or communication with the cyst. A distal pancreatectomy was performed under the diagnosis of mucinous cystadenocarcinoma. Grossly there was a brownish, hemispherical protrusion into the thin monolocular cyst. The cut surface of the protrusion showed a peripheral yellow-brownish area and an internal wine-colored area. Histopathologically the cyst wall consisted of tall columnar cells without atypical nuclei, ovarian-type stroma beneath the epithelium, and fibrotic tissue with abundant capillary vessels, suggestive of a mucinous cystadenoma. The protrusion was composed of peripheral organized hematoma without a covering epithelium, and internal hemorrhage and many capillary vessels, with no evidence of tumor cell necrosis. These histopathological findings appear to be similar to those of chronic expanding hematoma. The formation of a huge mural hematoma in a mucinous cystic neoplasm can occur as a repair process after the breaking of intrawall vessels.