Thecoma, a benign ovarian stromal tumour prevalent in postmenopausal women, characteristically appears as a well-defined enhancing solid mass with characteristic lipid-rich theca cells.
Description
Thecoma is a benign sex cord-stromal tumour of the ovary, characterised by the presence of lipid-rich theca cells. These tumours are most common in postmenopausal women and can occasionally cause symptoms due to hormone secretion, notably estrogen.
Pathogenesis
The precise pathogenesis of thecomas is unknown. They are believed to originate from the stromal cells of the ovarian cortex that differentiate into theca cells. Some thecomas have been associated with estrogen production, which can lead to endometrial hyperplasia or carcinoma.
Epidemiology, Risk Factors & Associations
- Thecomas are most commonly observed in postmenopausal women.
- Thecomas are associated with estrogen production in approximately 10-15% of cases, which can lead to endometrial hyperplasia or carcinoma.
Clinical Features
Clinical manifestations of thecomas can range from asymptomatic presentations to symptoms related to hormone production, such as abnormal uterine bleeding, endometrial hyperplasia, or endometrial carcinoma.
Complications
There is a minimal risk of malignant transformation. The risk of malignant transformation is not well-established due to the rarity of these tumours.
Pathological Features
Histopathology
- Macroscopic: Characteristically demonstrates yellowish, well-circumscribed masses.
- Microscopic: Demonstrates sheets of lipid-rich theca cells.
Serology
- No specific serologic markers are associated with thecomas.
Biochemistry
- Elevated levels of estrogen may be present in some cases.
Radiological Features
General Features
- Thecomas are typically seen as solid and well-defined masses.
- Calcifications can occur but are infrequent.
- Secondary features of hyperestrogenism, such as endometrial thickening, may be seen.
CT
- Non-contrast: Thecomas appear as hypodense masses.
- Contrast-enhanced: Significant enhancement is observed after contrast administration.
MRI
- T1WI: Demonstrates intermediate to high signal intensity.
- T2WI: May show high signal intensity due to cystic changes
- T1 C+: Enhancement is observed after contrast administration.
- DWI/ADC: No diffusion restriction is typically observed.
- In-out-of-phase: Signal drop on opposed-phase chemical shift imaging compared to in-phase, indicating the presence of intracellular lipid, a characteristic feature of thecomas.
US
- B-mode: Presents as a solid, hypoechoic mass with well-defined margins.
- Colour Doppler: Minimal vascularity is typically observed.
NM
- PET FDG: Thecomas are typically not FDG avid.
Grading and Staging
There is no specific grading or staging system for thecoma as it is a benign entity.
Diagnosis
The diagnosis of thecoma is predominantly made on histopathological examination following surgical excision of the tumour.
Differential Diagnosis
- Ovarian Fibroma: Tends to be whiter and firmer on gross examination. On imaging, both fibroma and thecoma may present similarly. Histological evaluation is definitive.
- Fibrothecoma: A mixed sex cord-stromal tumour with both fibroma and thecoma components. Histological examination provides definitive diagnosis.
- Leiomyoma: Commonly located within the uterus, and can often be differentiated based on its typical site and imaging characteristics.
- Ovarian Carcinoma: Tends to have a more aggressive appearance and behaviour, with complex solid and cystic morphologies often observed on imaging.
Management
The standard management of thecomas involves surgical resection, particularly for symptomatic individuals or when there is uncertainty in diagnosis. Depending on the patient’s age, fertility requirements, and the size of the tumour, surgical approaches may range from ovarian cystectomy to salpingo-oophorectomy.