Adenosquamous carcinoma arising in a mucinous cystadenoma of the pancreas.

Background: Approximately 500 cystic neoplasms of the pancreas have been reported, and among these the mucinous pancreatic cystadenomas are known to have malignant potential. We report a rare case of a mucinous cystadenoma containing adenosquamous carcinoma.

Methods: We studied the histochemical and immunohistochemical staining characteristics of the tumor by staining with hematoxylin/eosin, Alcian Blue/Periodic Acid Schiff, and with immunoperoxidase-labelled antibodies against carcinoembryonic antigen, epithelial membrane antigen, low and high molecular weight cytokeratins, the proliferation antigen Ki-67, and the tumor suppressor antigen p-53. The K-ras oncogene was analyzed by direct sequencing.

Results: This case illustrates the usual presentation and features of this unusual tumor-a middle aged woman with abdominal pain and no history of alcohol abuse or abdominal trauma. The mucinous cystic tumor of her pancreas was composed predominantly of benign epithelium with areas of a malignant component that were identified by thorough sampling.

Conclusion: We discuss the nomenclature of these neoplasms and suggest that continuing efforts to subclassify mucinous cystic pancreatic tumors histologically may not be necessary, since the tumors are all histologically similar and are malignant or have malignant potential, and for all, treatment should include resection.