MRI diagnosis of ovarian fibrothecomas: tumour appearances and oestrogenic effect features

Objective:

To study MRI diagnosis of ovarian fibrothecomas.

Methods:

MRI appearances of 27 ovarian fibrothecomas 26 female patients confirmed by surgical pathology were retrospectively reviewed and correlated with clinical and histological findings.

Results:

Most patients were post-menopausal females 73.1% (19/26) of cases. 38.5% (10/26) of patients showed an elevated serum carbohydrate antigen 125 (CA-125) level (>35 U ml⁻¹). On MR T₂ weighted imaging, 3 distinct features were revealed. (1) Homogeneous hypointense masses in 25.9% (7/27) cases. (2) Heterogeneous tumours with mostly isointense and few patchy hyperintense areas in 51.9% (14/27) cases. (3) Heterogeneous tumours with predominantly hyperintense and few isointense parts in 22.2% (6/27) cases. On T₁ weighted imaging, all the fibrothecomas turned out to be homogeneous masses except six cystic degeneration cases. After contrast, 70.4% (19/27) tumours showed homogeneous mild enhancement in all phases. Beyond the tumours, endometrial abnormality and uterus enlargement were found in 38.5% (10/26) and 15.4% (4/26) patients, respectively. Ascites were seen in 53.8% (14/26) patients. There was a statistically significant difference among the 3 T₂ weighted image features (F = 7.024; p = 0.003) in terms of the size of fibrothecomas. The cystic tumours also had the tendency to show the ascite condition (p = 0.002) as well as elevated serum CA-125 levels (p = 0.014). Vimentin was positively stained in 10 (76.9%) of 13 cases who underwent the immunohistochemical analysis.

Conclusion:

MRI has the superiority to show the distinct appearances of tumours as well as their functional features according to oestrogenic effect.

Advances in knowledge:

This study describes the unique features of fibrothecomas on MRI on a relatively large series of patients with tumours and the indirect oestrogenic effect findings.Fibrothecomas are rare benign ovarian tumours extending from solid fibromas to lipid-rich thecomas, making up approximately 4% of all ovarian neoplasms, while constituting the most common sex cord-stromal tumours of the ovary.¹ These tumours also account for the most common hormonally active ovarian neoplasms, which often show oestrogenic effects, and could present as uterine morphological changes and thickened endometrium, particularly in females of post-menopausal age.^2,3 Clinically, ovarian fibrothecomas are generally latent masses and might be detected occasionally during routine gynaecologic examinations. At gross inspection, fibrothecomas typically present as solid tumours with or without cystic degeneration. In pathology, fibrothecomas contain theca cells with abundant lipids in the cytoplasm and varying degrees of fibrous content, the theca cells may be responsible for the oestrogenic effects of the tumours. The intraperitoneal ascites or pleural effusions are often associated with fibrothecomas and might make them difficult to differentiate from malignant epithelial ovarian tumours. Correct diagnosis of these benign tumours can greatly affect the patient''s management, especially avoiding unnecessary invasive surgical procedures. So far, most of the previous studies^4,5 have reported non-specific ultrasound and CT features of these tumours, while MR studies^6,7 had only small sample sizes. The purpose of our study was to describe the unique features of fibrothecomas on MRI in a relatively large series of patients with tumours as well as to report indirect oestrogenic effect findings, and to discuss the points of differential diagnosis.