Gastrointestinal carcinoid tumors and second primary malignancies

The development of second primary malignancies (SPM) in patients with gastrointestinal carcinoid tumors is a well-described phenomenon, with reported rates as high as 55%. There is a predilection for gastrointestinal and genitourinary adenocarcinomas, but a variety of other malignancies have been reported as well. The etiology of this malignant predisposition may be rooted in the tumorigenic properties of the various neuroendocrine peptides elaborated and secreted by neuroendocrine cells. Peptides such as secretin, gastrin, bombesin, cholecystokinin (CCK), and vasoactive intestinal peptide (VIP) are believed to promote the growth of tumor cells. As many as 30 peptides and amines identified in neuroendocrine cells may have similar properties. This review of the literature on carcinoid-associated second primary malignancies is accompanied by a case report of metastatic carcinoid identified during surgical exploration for a perforating colon adenocarcinoma.