How are midgut carcinoid tumors characterized?

Updated: Feb 12, 2019
  • Author: Cameron K Tebbi, MD; Chief Editor: Max J Coppes, MD, PhD, MBA  more...
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In midgut carcinoids, cells are arranged in closely packed, round, regular, monomorphous masses. In the appendix, carcinoids appear as discrete yellow nodules in the lumen. Lesions associated with diffuse wall thickening are relatively uncommon. Carcinoid tumors commonly affect the tip of the appendix. Most carcinoid tumors invade the wall of the appendix, and lymphatic involvement is nearly universal. About 75% of patients have evidence of peritoneal involvement. However, only a few patients have regional or distant dissemination. The size of the tumor can be correlated with outcome of the disease; tumors smaller than 1.5 cm in diameter (after formalin fixation) rarely result in distant metastases or recurrences.

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