Appendiceal or cecal endometriosis with intestinal metaplasia: a potential mimic of appendiceal mucinous neoplasms

Appendiceal or cecal endometriosis uncommonly presents diagnostic challenges, but rare cases with intestinal metaplasia can mimic mucinous tumors of the appendix. We describe 6 cases of appendiceal or cecal endometriosis with intestinal metaplasia that grossly and microscopically mimicked appendiceal mucinous tumors. The cases were characterized by marked mural hypertrophy and elastosis, with distortion of the appendix, and virtual obliteration of the lumen of the appendix. All cases had conventional endometriosis, together with varying amounts of endometriosis with intestinal-type epithelium. In 2 cases, scant or virtually no stroma around some mucin-filled glands made their recognition as endometriosis more difficult. None of the cases had dysplasia of the mucinous epithelium. All patients had benign follow-up (mean 3.6 y). Endometriosis with intestinal metaplasia is a rare phenomenon that, when it occurs in the appendix or cecum, may lead to misdiagnosis as a low-grade appendiceal mucinous neoplasm or mucinous carcinoma.