Mucinous cystic neoplasm of the pancreas with neuroendocrine cells and malignant stroma.

Mucinous cystic neoplasms (MCN) with malignant sarcomatous stroma are rare aggressive tumors and there are few recorded cases. We report a case of MCN that had adenocarcinoma in situ and invasive adenocarcinoma with foci of sarcomatous stroma in a 40-year-old woman. Clear transition from adenocarcinoma areas into sarcomatoid foci was noted. The stromal component showed immunoreactivity for CK7 and Cam 5.2 supporting epithelial origin of the sarcomatoid areas. Associated areas of cytologically benign MCN epithelium were present and were immunoreactive for positive staining with pan-cytokeratin (AE1/AE3), cytokeratin 7 (CK 7), cytokeratin 20 (CK 20), pan-cytokeratin (Cam 5.2), epithelial membrane antigen (EMA), muscle specific actin (MSA), and carcino-embryonic antigen (CEA). Interestingly, definite scattered pear-shaped neuroendocrine cells, as evidenced by strong immunoreactivity for chromogranin and synaptophysin, were identified in the cytologically benign MCN lining but not in the malignant epithelial component. We found that these tumor cells probably arise from a single precursor cell capable of divergent differentiation.