Myofibroblastoma of the ovary: Report of a case

We report an unusual case of an ovarian tumor arising in a 22-year-old fema le that showed histologic, immunohistochemical, and ultrastructural feature s of myofibroblastic differentiation. The mass was found incidentally and u pon excision was 9.0 cm in its greatest dimension and almost entirely repla ced the left ovary. The patient is alive without evidence of disease 21 mon ths after excision, Histologically, the tumor was encapsulated and composed of cytologically bland spindled cells arranged into a variety of patterns, similar to those found in both solitary fibrous tumor and hemangiopericyto ma, Immunohistochemically, the cells stained strongly for smooth muscle act in and muscle-specific actin, with only focal and weak staining for CD34. S tains for S-100 protein, desmin, and AE1/ AE3 were negative. Ultrastructura lly, the neoplastic cells showed clear-cut evidence of myofibroblastic diff erentiation. The differential diagnostic considerations, including solitary fibrous tumor and hemangiopericytoma, are discussed.