An unusual malformation of the vermiform appendix simulating endometriosis: a case report with discussion of differential diagnosis.

A 48-year-old nulliparous woman with a long history of pelvic endometriosis underwent a gynecologic operation, and a swollen and indurated appendix was removed because of suspected endometriosis. Pathologic examination revealed no endometriosis, but examination of the distal appendix showed structural disorganization of its entire wall, with lack of proper differentiation of its normal coats and irregular overgrowth of fibroadipose, fibromuscular, and neural elements. Differential diagnoses, including endometriosis, carcinoid tumor and neurofibromatosis, are discussed.