By Jason Wasserman MD PhD FRCPC
June 7, 2023
Ovarian fibroma is a non-cancerous type of ovarian tumour. It develops from the stromal cells normally found inside the ovary. These tumours can range in size from less than 1.0 cm to over 20 cm.
Most ovarian fibromas do not cause any symptoms and the tumour is found incidentally when imaging of the pelvis is performed for other reasons or when the ovary is removed for other reasons. Large ovarian fibromas can cause symptoms such as pain or abdominal pressure.
The diagnosis of ovarian fibroma is usually made after the entire ovary is surgically removed and sent to a pathologist for examination under the microscope.
Microscopically, the tumour is made up of long thin cells called spindle cells. The spindle cells are usually arranged in branching groups called fascicles and are surrounded by dense connective tissue that may be described as hyalinized or fibrotic. A small number of dividing tumour cells called mitotic figures may also be seen. Large tumours or those that have been present for a long time may undergo a series of degenerative changes including hemorrhage (bleeding into the tumour) and infarct-type necrosis (cell death as a result of decreased blood flow). Tumours with a greater density of tumour cells (the number of cells in a given area of tissue) are called cellular fibromas while those that show an increased number of mitotic figures are called mitotically active cellular fibromas.
Your pathologist may perform a test called immunohistochemistry to confirm the diagnosis. When immunohistochemistry is performed, the tumour cells in an ovarian fibroma are often positive for inhibin, calretinin, WT1, and the hormone receptors estrogen receptor (ER) and progesterone receptor (PR).