Neuroendocrine carcinomas of the colon and rectum: a clinicopathologic evaluation.

Neuroendocrine carcinomas were diagnosed in 13 of 683 patients who had colon cancers removed from January 1980 to June 1987 for an incidence of 1.9%. The patients were 28 to 89 years of age (median, 72 years). There were seven male and six female patients. The treatment was as follows: right hemicolectomy, 5; transverse colectomy, 1; left hemicolectomy, 1; low anterior resection, 2; abdominal-perineal resection, 1; and in 3 patients with rectal tumors, biopsy examination only was performed. Microscopic stages were as follows: Dukes' stage B, 1; stage C, 6; stage D, 5; and stage indeterminate, 1. By light microscopy, the tumors showed solid clusters or ribbons of round to fusiform, small to intermediate-sized cells with variably abundant mitoses. Eight tumors had foci of glandular and/or squamous differentiation. By immunohistochemistry, all tumors showed one or more neuroendocrine markers, including neuron-specific enolase, chromogranin, synaptophysin, serotonin, and various neuropeptides. By electron microscopy, single membrane-bound neurosecretory granules were noted. The sites of metastases included regional nodes, 8; liver, 5; bone, 1. Four patients were treated with a combination of chemotherapy and radiation therapy. These tumors were, as a group, aggressive, with eight patients dead within 12 months of diagnosis. Median survival was 7 months, with three patients alive at 2, 38, and 68 months, respectively. Specifically, small- and intermediate-cell neuroendocrine carcinomas of the colon and rectum behaved very aggressively and displayed numerous structural and functional similarities with their bronchopulmonary counterparts.