Electron microscopic study of mucoepidermoid carcinoma in the pancreas.

An autopsy case of extremely rare mucoepidermoid carcinoma of the pancreas in a 58-year-old male was reported. The main tumor in the pancreatic tail associated with wide-spreading metastases, was histologically composed of squamous cancer cell nests intermingled with mucin-containing cells, but not true glandular structures except for metastatic foci in the liver. Electron microscopic findings of the main tumor revealed roughly three kinds of cancer cells, namely undifferentiated cells, squamous cells, and squamous cells with mucin-containing intracytoplasmic lumina, accompanied by variety of transitional forms. The mucin was similar to that of the intra-or interlobular duct epithelium of pancreas in mucin stains. Immunohistochemically, positive immune reaction of the cancer cells was observed by anti-keratin, -epithelial membrane antigen and -carcinoembryonic antigen sera. These findings suggested that the cancer cells originated from undifferentiated cells of pancreatic duct, which showed multipotency to differentiate predominantly into squamous cells, but also into mucin-producing cells.