Ovarian fibroma

Last revised by Candace Makeda Moore on 30 Dec 2024

Ovarian fibromas are benign ovarian tumors of sex cord/stromal origin. Although fibromas account for ~4% of all ovarian neoplasms, they are the most common sex cord ovarian tumors.

Fibromas occur at all ages but are most frequently seen in middle-aged women.

They are associated with ascites in 40% of cases and with pleural effusions in a small percentage of cases. 

Fibromas are generally asymptomatic and are often detected at palpation during a routine gynecologic examination. Tumors can reach a large size at presentation.

The tumor belongs to the same histopathologic spectrum as an ovarian thecoma/ovarian fibrothecoma. Fibromas have no (or very few) thecal cells and no (or minimal) estrogen activity.

It is composed of spindle cells forming variable amounts of collagen. Sectioning of a fibroma typically reveals a chalky-white surface that has a whorled appearance, similar to that of a uterine fibroid. Areas of edema, occasionally with cyst formation, are also relatively common.

On ultrasound, fibromas most commonly manifest as solid, hypoechoic masses with ultrasound beam attenuation. As such, they may appear similar to a pedunculated subserosal uterine fibroid.

However, the sonographic appearance can be variable, and some tumors can rarely have cystic components.

Fibromas usually manifest as diffuse, slightly hypoattenuating masses with poor, very slow contrast enhancement. Calcification and bilaterality are both uncommon.

  • T1: usually demonstrate homogeneous low signal intensity 

  • T2

    • appear as well-circumscribed masses with low signal intensity

    • may contain scattered hyperintense areas representing edema or cystic degeneration

    • a band of T2 hypointensity separating the tumor from the uterus on all imaging planes is considered a characteristic feature

  • DWI: hypointense

  • T1 C+ (Gd): usually shows heterogeneous enhancement 5

On dynamic contrast-enhanced MRI, enhancement of the fibromas and fibrothecomas is lower than that of myometrium and fibroids

Ovarian fibromas are categorized as O-RADS MRI 2 2.

Ovarian fibromas are almost always benign 3.

General imaging differential considerations include:

  • large pedunculated subserosal uterine leiomyoma

  • thecoma and fibrothecoma

    • tend to have brighter signal on T2 given edema and cystic degeneration

    • contrast-enhancement may be observed given the vascularization of the theca cells

  • Brenner tumor

    • calcification more common

    • associated with another epithelial tumor in ipsilateral or contralateral ovary in some cases

    • may have cystic components

    • solid components show contrast enhancement

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