Ovarian fibroma, the most common benign solid tumour of the ovary, is frequently seen in postmenopausal women and may be associated with Meigs syndrome. It appears as a solid, hypointense mass on T1 and T2-weighted MRI.
Description
Ovarian fibroma is a benign, solid, sex cord-stromal tumour that is composed mostly of fibrous tissue. It is the most common benign solid tumour of the ovary and can occur at any age, but predominantly seen in postmenopausal women.
Pathogenesis
The pathogenesis of ovarian fibroma is not well understood. As a sex cord-stromal tumour, it originates from the stromal cells that surround the ovarian follicles. These cells undergo neoplastic transformation to form a fibroma.
Subtypes
There are no well-recognised subtypes of ovarian fibroma.
Epidemiology, Risk Factors & Associations
- Ovarian fibroma is associated with postmenopausal status.
- There is an association with Gorlin syndrome (nevoid basal cell carcinoma syndrome) in which multiple bilateral fibromas may occur.
Clinical Features
The clinical presentation of ovarian fibroma is often non-specific. Patients may present with abdominal pain or a palpable mass. A unique clinical feature associated with ovarian fibroma is Meigs syndrome, characterised by the triad of ovarian fibroma, ascites, and pleural effusion.
Complications
There is rare risk of malignant transformation to fibrosarcoma (~1%).
Pathological Features
Histopathology
- Macroscopic: Ovarian fibromas are solid, firm, white or tan tumours that may be small or large.
- Microscopic: Histologically, they consist of bland spindle cells arranged in a storiform pattern.
Serology
- CA-125 may be slightly elevated.
Biochemistry
- No specific biochemical markers.
Radiological Features
General Features
- Characteristically demonstrates solid ovarian mass with a homogenous texture. Often associated with minimal ascites. Calcification can be seen in about 10% of cases.
CT
- Non-contrast: Fibromas appear as well-defined, solid, hypoattenuating masses.
- Contrast-enhanced: They show minimal enhancement.
MRI
- T1WI: Low to intermediate signal intensity.
- T2WI: Low signal intensity, which is a characteristic feature.
- T1 C+: Minimal enhancement.
- DWI/ADC: No restriction.
US
- B-mode: Hypoechoic, solid mass.
- Colour Doppler: Minimal vascularity.
NM
- PET FDG: Usually not FDG avid.
Grading and Staging
No specific grading or staging system exists for ovarian fibroma, as it is a benign tumour.
Diagnosis
Diagnosis of ovarian fibroma is usually confirmed by histopathological examination after surgical excision.
Differential Diagnosis
Imaging-based
Other ovarian or adnexal lesions with low T2 MR signal:
- Fibrothecoma/Thecoma: A benign ovarian tumour that contains both fibrous tissue and thecal cells, which are hormone-producing cells (oestrogen). Typically appears as hypoechoic on ultrasound, shows bright signal on T1W and dark signal on T2W MRI. It often enhances moderately after contrast administration.
- Cystadenofibroma: A benign ovarian tumour that has both cystic and fibrous components. These tumours can have a more complex structure compared to simple fibromas or fibrothecomas, often presenting with a mixture of solid and cystic areas.
- Brenner Tumour: An uncommon epithelial-stromal tumour. Fibrous components and calcifications (if present) are markedly hypointense of T2.
- Uterine Leiomyoma: Found in the uterus, not in the ovary, and can often be differentiated based on location. Exophytic subserosal leiomyoma can have low T2 signal with low to intermediate T1 signal on MRI. The bridging vessel sign represents tortuous vascular structures passing between the uterus and the lesion, and confirms the lesion originates from the uterus, not the ovary. It is best seen on post-gadolinium MRI, which demonstrates vascular flow voids. Can also be seen on US.
- Ovarian carcinoma: More often demonstrates a complex solid and cystic morphology, with a more aggressive appearance and behaviour.
Management
Management typically involves surgical excision, especially in symptomatic cases or when the diagnosis is uncertain. The procedure may range from ovarian cystectomy to salpingo-oophorectomy, depending on the size of the tumour and the patient’s age and fertility requirements.