Clinicopathologic findings in gynecologic proliferations of the appendix

Appendiceal endometriosis, endosalpingiosis, and decidual lesions have received little attention in the pathology literature, meaning their clinicopathologic features remain unclear. We identified 72 cases of appendiceal gynecologic proliferations with available slides. Clinical presentation was recorded when available, and histologic findings were correlated with clinical data. Cases included conventional endometriosis (51), endosalpingiosis (14), and decidual lesions (7). The patients with endosalpingiosis were significantly older (median 45 years) than those with endometriosis (median 34 years, P = .0085) or decidual lesions (median 31 years, P = .0088). Most endometriosis patients presented with known/suspected endometriosis (20/51, 39%), while acute appendicitis was the most common presentation for patients with endosalpingiosis (5/14, 36%) or a decidual lesion (5/7, 71%). Few patients presenting with appendicitis were ever diagnosed with extra-appendiceal disease. All 51 endometriosis cases showed both glands and stroma, and 18 (35%) had hemosiderin. One case progressed to endometrioid adenocarcinoma. Endosalpingiosis was an incidental finding in all cases, confined to the serosa in 4 and extending intramurally in 10. Four of the 7 patients with a decidual lesion were pregnant, and 2 others were taking oral contraceptives. The cases included florid decidualized endometriosis (5) and deciduosis (2). Two cases spread transmurally and effectively obliterated the appendix. Conventional appendiceal endometriosis can have several clinical presentations. Patients with it who present with acute appendicitis rarely develop it elsewhere. Appendiceal endosalpingiosis is rare and effectively incidental. Decidualized endometriosis may overtake the entire appendix.