Neuroendocrine tumors of the rectum: a 10-year review of management

Neuroendocrine tumors of the rectum constitute approximately 19 per cent of gastrointestinal neuroendocrine tumors (NETs). The histologic characteristics of the tumor seem to be an indicative prognostic factor. Optimal treatment of NETS of the rectum has been widely debated, but more recent studies suggest that treatment depends upon the size. The medical records of 37 patients with NETS of the rectum were retrospectively reviewed. We reviewed their presentation, surgical treatment, pathology, and outcome. All pathological specimens were reviewed. Neuroendocrine tumors of the rectum were classified as either well-differentiated tumors, well-differentiated neuroendocrine carcinoma, or poorly differentiated neuroendocrine carcinoma. Evaluating tumor size, we found 35/37 patients had tumors less than 1 cm, 1 patient had a tumor between 1 and 2 cm, and one had a tumor greater than 2 cm. Pathologic evaluation of the tumors revealed that 35 of the tumors invaded the submucosa only, one invaded the muscularis propria, and one invaded the perirectal adipose tissue. The histopathologic features of the tumors revealed that 34 of the tumors were well-differentiated NETS with benign features, one tumor had invaded the submucosa, with angioinvasion, and two tumors were neuroendocrine carcinoma. Thirty-five patients underwent local excision. Eleven had reexcisions for positive margins. Two patients had local excision for recurrence, and one patient underwent low anterior resection (4 cm). Twelve patients had negative margins, 25 had positive margins. Eleven patients underwent reexcision. Six had no evidence of residual disease, and five had persistent positive margins and were offered no further treatment. Nineteen patients had positive margins and did not have reexcision. They all had tumors < 1 cm. Despite half of the lesions being resected with final pathologic positive margins, we have seen no significant influence on recurrence or overall survival. This raises the question of margin clearance in early lesions.