The most common benign solid tumor of the ovary is the fibroma ( about the 4% of all ovarian tumors )
Fibromas are derived from connective tissue and arise from the solid ovarian cortical stroma.
The stroma of the ovary consists of undifferentiated mesenchymal cells and their endocrine derivatives.
Fibromas, thecomas, fibrosed thecomas, and fibrothecomas are ovarian tumors of gonadal stromal origin and may be variants of a single entity.

Cellular fibroma of Ovary is an uncommon benign ovarian neoplasms.

It mimics fibrosarcoma histologically because of its rich cellularity and high number of mitoses.
Cellular fibroblastic tumors of the ovary are currently classified as either cellular fibroma or fibrosarcoma. The former are characterized by bland nuclei, 3 or fewer mitotic figures per 10 high-power fields
Women with these tumors are generally asymptomatic, and masses are typically detected in middle-aged women at palpation during routine gynecologic examination. A gain of trisomy 12 cells has been demonstrated by FISH in eight of these tumor.

Greater than 90% are unilateral, and approximately 10-15% are found in association with ascites.
One percent of cases are associated with Meigs syndrome, characterized by ovarian fibroma, ascites, and pleural effusion.

Ultrasonographically, these tumors appear hypoechoic with attenuation of the ultrasound beam.
CT demonstrates a well-defined solid homogeneous or mildly heterogenous mass with little or no enhancement.
The tumours can grow to a large size and demonstrate cystic degeneration and dystrophic calcification.
The malignant potential is reported to be under 1%.