Leiomyomatosis peritonealis disseminata with malignant change in a man

Leiomyomatosis peritonealis disseminata (LPD) is a rare clinicopathological entity typically observed in women of reproductive age. We report a case of LPD with malignant change in a man. A 77‐year‐old man presented with a mass measuring 10 cm in diameter at the terminal ileum and numerous peritoneal small nodules that were revealed by abdominal computed tomography. Right hemicolectomy with lymph node dissection was performed. Macroscopically, a tumor of the terminal ileum consisted of aggregates of small nodular lesions with calcification and necrosis. The wall of the ileum and colon was intact. Microscopically, some of the nodular lesions consisted of neoplastic growths of atypical spindle cells with cellular atypism and abnormal mitoses. A few of these lesions were completely surrounded by smooth muscle bundles. Hemorrhages and necroses were found within the tumor nodules. Immunohistochemically, the tumor cells were positive for vimentin, desmin, muscle actin, α‐smooth muscle actin, cytokeratin and p53. The remaining nodular lesions, including small peritoneal lesions, were composed of hypocellular hyalinizing nodules. This case was thought to be LPD with malignant change, although the pathogenesis was uncertain because the tumor cells were negative for estrogen and progesterone receptors.