Fibromas are the most common sex cord-stromal tumour. While they can occur at any age, it is a disease generally of middle-aged women. It is uncommon in women aged < 30 years - in such a context, it would be prudent to clinically consider Gorlin syndrome. In the setting of Gorlin syndrome, the fibromas are frequently bilateral, multinodular, and calcified. None of these features were present in this patient.

The lesion is composed fo uniform spindle cells forming short fascicles and storifiorm arrangements. Cytoplasm is scanty, with uniform, oval-to-elongated wavy nuclei. Focal luteinization and thecal components can be observed.

Unusual features that may be observed include increased cellularity ("cellular fibroma"), increased mitotic activity (> 3/10 HPFs), intracytoplasmic hyaline droplets, bizarre nuclei, and Verocay-like areas. In this case, however, all of these features were absent.

Differential diagnoses include synovial sarcoma, ovarian fibrosarcoma, leiomyoma, and sclerosing stromal tumour.

This slide shows inhibin stain. See related content for H&E, SMA,and calretinin stains.

Another example of ovarian fibroma is described in LMP95285 (see Related Content).