Heterotopic pancreas in the spleen: malignant degeneration to mucinous cystadenocarcinoma.

We report the clinicopathological findings of a patient who presented with a primary splenic cystic tumour arising from heterotopic pancreatic tissue. The pancreas was normal on radiological and intraoperative examination. Histological analysis of the specimen demonstrated a mucinous cystadenocarcinoma with remnants of normal pancreatic tissue within the substance of the spleen. Immunohistochemistry characterized the tumour as being pancreatic in origin with overexpression of p53 protein. Five cases of primary mucinous cystadenocarcinoma of the spleen originating from heterotopic pancreatic tissue have been described; to our knowledge, this is the first case to provide conclusive immunohistochemical evidence to support this proposition.