Anatomic Pathology / ORIGINAL ARTICLE

A b s t r a c t This report documents 2 cases of obstructive mucocele of the appendix secondary to endometriosis of the appendix. In 1 case, the tip of the mucocele was ruptured and associated with localized pseudomyxoma peritonei. Mucoceles of the appendix usually are associated with hyperplastic or neoplastic mucosal proliferation; obstruction, particularly that due to endometriosis, is an infrequent cause. Occurrence of localized pseudomyxoma peritonei associated with appendiceal endometriosis and mucocele has not been reported previously. The majority of mucoceles of the appendix are caused by epithelial lesions associated with excess mucin produc-tion. Such lesions include hyperplastic polyps, mixed hyperplastic-adenomatous polyps, adenomas, and adenocar-cinomas. A minority of appendiceal mucoceles are caused by mucous distention secondary to obstruction of the appendix—so-called obstructive, retention, or simple muco-celes. Obstruction can be due to fecaliths, postinflammatory scarring, or rarely, endometriosis. Irrespective of cause, rupture of a mucocele may lead to pseudomyxoma peritonei (PMP), ie, the presence of mucinous material in the peri-toneal cavity. We describe 2 cases, of obstructive mucocele secondary to endometriosis; in 1 case there was rupture of the appendix and localized PMP. Materials and Methods The surgical specimens were fixed in 10 % neutral buffered formalin, and representative sections (except as indicated) were processed by conventional methods. Sections cut at 5 µm were stained with H&E; some sections were stained with periodic acid–Schiff with diastase diges-tion.