NEUROENDOCRINE CANCERS OF THE COLON AND RECTUM - RESULTS OF A 10-YEAREXPERIENCE

PURPOSE: Our goal was to define the incidence of neuroendocrine carcin omas of the colon and rectum, the patterns of neuroendocrine expressio n, and the cellular subtype within neuroendocrine tumors. We attempted to determine whether differences in neuroendocrine expression or spec ific cell type influenced survival. METHODS: Over a ten-year period, 9 88 patients had resections for colorectal cancer. Using immunohistoche mical staining methods specific for neuroendocrine markers, 39 (3.9 pe rcent) neuroendocrine cancers were identified retrospectively. Tumors were also stained with monoclonal antibody A-80 which is specific for exocrine differentiation. In this way we were able to determine the ex tent of neuroendocrine differentiation such as pure neuroendocrine, pr edominant neuroendocrine, and equal neuroendocrine-exocrine expression . RESULTS: Average patient age was 65.5 (range, 28-89) years; there we re 25 males and 14 females. Nineteen tumors were located in the right colon, 11 in the left, and 9 were in the rectum. Three histopathologic patterns were identified: pure neuroendocrine (n = 11), predominantly neuroendocrine (n 17), and cancers with equal exocrine and neuroendoc rine differentiation (n = 7). Three cellular subtypes were seen: small -cell (n 15), intermediate-cell (n = 15), and well-differentiated neur oendocrine cancers (n = 5). There was one Dukes A cancer, 7 Dukes B, 1 6 Dukes C, and 15 patients had metastases to distant sites at the time of diagnosis. As a group, neuroendocrine tumors have a poor prognosis : six-month survival was 58 percent, three-year survival was 15 percen t, and five-year survival was 6 percent. Survival statistically correl ated with tumor stage (P = 0.01) but not with age, sex, tumor location , histopathologic pattern, or neuroendocrine subtypes. Median survival for pure neuroendocrine carcinomas was seven months and for predomina ntly neuroendocrine carcinomas was five months. Tumors with equal neur oendocrine and exocrine differentiation had a median survival of 22 mo nths (P = 0.3). Small-cell neuroendocrine carcinomas had a median surv ival of five months, intermediate-cell had 11 months, and well-differe ntiated had a median survival of 22 months (P = 0.1). CONCLUSIONS: Neu roendocrine differentiation is found in at least 3.9 percent of colon and rectal cancers. Many of these tumors were initially diagnosed as ' 'carcinoids,'' the diagnosis was changed to ''neuroendocrine carcinoma '' after immunohistochemical staining. Overall survival is poor especi ally for small-cell and pure neuroendocrine carcinomas.