Cellular Fibromatous Neoplasms of the Ovary.

Many ovarian tumors composed primarily of fibroblastic cells are fibromas of usual type, and generally do not pose diagnostic difficulty. These tumors can be diagnosed accurately in most instances based on morphology without needing immunohistochemistry. Approximately 10% of fibromatous neoplasms, however, exhibit increased cellularity and mitotic activity, and, in the presence of the former or both features, are classified as cellular fibroma or mitotically active cellular fibroma. Distinguishing these entities from fibrosarcoma, an exceptionally uncommon ovarian malignancy, is important. This article reviews fibromatous ovarian tumors, emphasizing cellular fibromas and their differential diagnosis.