[A case of large cell neuroendocrine carcinoma of the rectum].

A 77-year-old woman was referred to our hospital because of blood in feces and anal pain. Colonoscopy revealed a villous semicircular tumor in the rectum. A biopsy showed well-differentiated adenocarcinoma. Miles' operation was performed because of the persistence of anal pain and blood in feces. Histological and immunohistochemical analysis showed coexistent tubulovillous adenoma, tubulovillous adenocarcinoma, and large cell neuroendocrine carcinoma (LCNEC), which was positive for CD56, chromogranin A, and synaptophysin. Pathological examination revealed that most of the lesion was occupied by the LCNEC. The tumor was therefore diagnosed as LCNEC of the rectum. The patient underwent adjuvant chemotherapy with cisplatin (CDDP), irinotecan (CPT-11), and mFOLFOX6, but died because of LCNEC progression 10 months after the operation. LCNEC rarely occurs in the gastrointestinal tract; here we report a case of rectal LCNEC.

Gastric undifferentiated carcinoma with diffuse c-kit overexpression and focal neuroendocrine differentiation.

A case of gastric undifferentiated carcinoma with diffuse c-kit overexpression and focal neuroendocrine differentiation is described. A 76-year-old man presented appetite loss for 1 month. Gastric endoscopy showed an exophytic huge nodular mass with central ulceration at the gastric prepylorus. Distal gastrectomy was performed with lymph node dissection. Histology indicated anaplastic medium- to large-sized round tumor cells in discohesive sheets. Adenocarcinomatous areas forming tubular glands or with intracytoplasmic mucin on PAS and Alcian-blue staining were not found in any sections. Immunohistochemistry showed that the tumor cells were diffusely positive for cytokeratin, vimentin, c-kit and focally positive for chromogranin A and synaptophysin. We hypothesized that c-kit overexpression of this tumor was attributed to neuroendocrine differentiation.