Leiomyomatosis peritonealis disseminata: immunohistochemical profile and origin

Leiomyomatosis peritonealis disseminata (LPD) is a rare disease presenting as multiple peritoneal nodules of smooth muscle cells, mimicking peritoneal carcinomatosis. This disease usually pursues a benign course. We report one case of LPD in a 32-year-old woman, G2PI, without gynecological history. At term, she had an elective caesarean section during which several firm peritoneal nodules, ranging from 0.2 to 0.4 mm, were found. Microscopic examination showed a smooth-muscle cell proliferation with no mitosis, no atypia and no necrosis. Immunohistochemical analysis showed diffuse and strong staining for progesterone receptors and partial expression of estrogen receptors. The cells coexpressed smooth muscle actin, desmin, h-caldesmon, calretinin, WTI, and CD117 (KIT). They were weakly positive for EMA but negative for CD34. Proliferation index was low with 5% of cells being positive for MIB-I. This case of LPD proved to have an unusual immunohistochermistry profile raising the question of its real origin.