Appendiceal mucinous cystadenoma is a neoplastic complication of IBD: Case-control study of primary appendiceal neoplasms

Background: IBD is a risk factor for development of colorectal neoplasia. Although IBD frequently involves the appendix microscopically, it is uncertain whether it also predisposes to appendiceal neoplasia. Methods: We performed a retrospective case-control study of incidental appendiceal neoplasms in colectomy specimens of adults with and without IBD (cases and controls, respectively) based on surgical pathology records spanning 54 months. To minimize referral bias, patients were excluded if they had preoperative clinical evidence or a principal pathologic diagnosis of appendiceal disease. The pathologic diagnoses were confirmed retrospectively. Results: Eleven appendiceal cystadenomas and 6 appendiceal carcinoid tumors were identified among 705 IBD cases (377 ulcerative colitis, 317 Crohn's disease, 11 indeterminate colitis) and 498 non-IBD controls meeting our inclusion criteria. There was no significant difference in prevalence of cyst adenomas between the cases and controls (9/705 [1.3%] versus 2/498 [0.4%], respectively, OR 3.2 [95% CI 0.7-14.9]). However, cyst adenomas were 15-fold more prevalent among cases with synchronous colorectal neoplasia compared with controls (4/69 [5.8%] versus 2/498 [0.4%], OR 15.3 [95% CI 2.7- 85]) and 8-fold higher compared with cases without synchronous neoplasia (4/69 [5.8%] versus 5/636 [0.8%], OR 7.8 [95% CI 2.0-29.6]). Appendiceal carcinoids were equally prevalent in cases and controls (4/705 [0.6%] versus 2/498 [0.4%], OR 1.4 [95% CI 0.3-7.8]), cases with synchronous neoplasia and controls (1/69 [1.4%] versus 2/498 [0.4%], OR 3.6 [95% CI 0.3- 40.8]), and cases with and without synchronous colorectal neoplasia (1/69 [1.4%] versus 3/636 [0.5%], OR 3.1 [95% CI 0.3-30.2]). Conclusions: IBD with synchronous colorectal dysplasia or cancer is a risk factor for development of appendiceal cystadenomas, implicating this tumor as a neoplastic complication of IBD. IBD does not predispose to the development of appendiceal carcinoids.