Neuroendocrine neoplasms arising in inflammatory bowel disease: a report of 14 cases.

Inflammatory bowel disease (IBD), particularly ulcerative colitis (UC), is a premalignant condition, because these patients are at increased risk of adenocarcinoma. Neuroendocrine neoplasms (NENs) have rarely been described in this setting. We evaluated 14 cases of NEN arising in a setting of IBD. All of the tumors arose in areas involved by IBD, and all showed immunohistochemical or ultrastructural evidence of neuroendocrine differentiation. The cohort included seven men and seven women (range, 28-71 yr; median, 43 yr). Eight patients had Crohn's disease (CD), and six had UC. Duration of disease ranged from 4 months to 50 years (median, 15 yr), with one of unknown duration. Of the eight patients with CD, five had ileocolitis, one had ileitis, one had colitis, and in one case, the extent of disease was unknown. Of the six patients with UC, four had extensive UC, one had left-sided UC, and the extent of UC was unknown in one case. Reasons for surgery included CD complications (five patients), refractory disease (three patients), dysplasia/carcinoma (five patients), and incontinence (one patient). The NENs were well differentiated in 11 cases and poorly differentiated mixed adenocarcinoma/small cell carcinomas in 3 cases. Tumor sites included the rectum (six cases), appendix (four cases), small bowel (two cases), and sigmoid colon (two cases). High-grade dysplasia was present in adjacent mucosa in four cases, and low-grade dysplasia was present in distant mucosa in two cases. Two patients with poorly differentiated NENs died from the disease at 3 and 11 months after tumor excision. All of the other patients were alive without tumor as of last follow-up. We concluded that NENs rarely arise in a setting of IBD. Most are well-differentiated tumors and are clinically indolent. Dysplasia is found in adjacent mucosa in more than one-third of cases, suggesting that neuroendocrine differentiation might evolve from multipotential cells in dysplastic epithelium.