Ovarian thecoma is a benign sex cord-stromal tumor originating from the theca cells of the ovarian stroma. Unlike fibroma, it is hormonally active — producing estrogen that can cause endometrial hyperplasia and abnormal uterine bleeding. On imaging, it appears as a solid mass; on MRI it shows slightly higher T2 signal than fibroma (more lipid and water content). On CT, it shows soft tissue density with poor-to-moderate enhancement. It generally occurs in postmenopausal women (60%). It is unilateral and well-defined. Malignant transformation is extremely rare. Treatment is surgical excision; hormonal symptoms resolve after surgery.
Age Range
50-70
Peak Age
60
Gender
Female predominant
Prevalence
Uncommon
Thecoma originates from the theca cells of the ovarian stroma. Theca cells are normally responsible for estrogen production in the follicular wall — tumoral proliferation maintains this function and secretes excessive estrogen. This estrogen excess causes endometrial stimulation → endometrial hyperplasia → postmenopausal bleeding. Theca cells contain intracellular lipid droplets — this lipid content directly affects imaging: higher T2 signal than fibroma (lipid protons lengthening T2 + increased intracellular water), sometimes mild T1 hyperintensity (lipid effect). On CT, it appears as soft tissue density but may be slightly lower density than fibroma (lipid effect). Enhancement is more prominent than fibroma because theca cells form a more vascular tumor than fibroblasts. Fibrothecoma (mixed type) contains both fibrous and thecal components — imaging features are intermediate.
Detection of endometrial thickening (postmenopausal >5 mm, premenopausal above normal for secretory phase) together with a solid ovarian mass strongly suggests an estrogen-producing tumor. Thecoma is the most common estrogen-producing ovarian tumor. This association is critically important for differentiation from fibroma — fibroma does not produce hormones, endometrial thickening is not expected. Granulosa cell tumor can also produce estrogen but is distinguished by its solid-cystic mixed structure and more aggressive course.
Homogeneous solid lesion between hypoechoic and isoechoic. May be slightly more echogenic than fibroma (lipid content). Well-defined, oval or round shape. Cystic component is generally absent. Accompanying finding: endometrial thickening (>5 mm postmenopausal) — estrogen effect.
Report Sentence
A ___ x ___ mm well-defined, homogeneous hypoechoic-to-isoechoic solid lesion is seen in the right/left ovary; accompanying endometrial thickening (___ mm) is present.
Minimal to moderate vascularity on Doppler. Relatively more vascularity than fibroma may be seen. Intratumoral and peripheral thin vascular structures may be visible. No ring-of-fire pattern. Intense, chaotic vascularity belongs to malignant solid tumors.
Report Sentence
Minimal to moderate intratumoral vascularity is seen in the solid lesion on Doppler examination.
Intermediate-to-low signal intensity on T2W — slightly higher signal than the marked hypointensity of fibroma. Isointense to mildly hyperintense compared to muscle. Homogeneous or mildly heterogeneous signal. This signal difference is the most valuable MRI finding for thecoma-fibroma differentiation.
Report Sentence
A solid mass measuring ___ x ___ mm showing signal isointense to mildly hyperintense to muscle is seen in the right/left ovary on T2W; consistent with thecoma.
Intermediate signal on T1W, isointense to muscle. Sometimes mildly hyperintense foci may be seen due to lipid content. Signal loss occurs in these hyperintense foci on fat-sat sequences — confirming intracellular lipid presence.
Report Sentence
The solid lesion shows signal isointense to muscle on T1W with focal hyperintense areas losing signal on fat-sat sequence (intracellular lipid).
Well-defined solid mass of soft tissue density (35-55 HU) on CT. Enhancement is poor to moderate — slightly more prominent than fibroma. Homogeneous or mildly heterogeneous enhancement. Calcification is rare. Accompanying findings: endometrial thickening, ascites (rarely).
Report Sentence
A ___ x ___ mm solid mass of soft tissue density with poor-to-moderate enhancement is seen in the right/left ovary.
Mild diffusion restriction may be seen on DWI (due to cellular structure). ADC values are slightly lower than fibroma (higher cellularity). However, it differs from marked diffusion restriction in malignant tumors — ADC values are at an intermediate level.
Report Sentence
Mild diffusion restriction is seen in the solid lesion on DWI with intermediate ADC values.
Criteria
Composed entirely of theca cells. Minimal fibrous component. Estrogen production is prominent.
Distinct Features
Significantly higher T2 signal than fibroma. Lipid foci may be more prominent on T1. Enhancement better than fibroma. Endometrial thickening frequently accompanies.
Criteria
Contains both fibrous and thecal components. Most common variant. Imaging: intermediate features between fibroma and thecoma.
Distinct Features
T2 signal slightly higher than fibroma, lower than pure thecoma. Hormonal activity variable — endometrial thickening may or may not be present. Enhancement poor to moderate.
Criteria
Theca cells in luteinized (steroid active) appearance. Generally in younger women. Androgen production may also occur (virilization).
Distinct Features
More heterogeneous appearance — may contain cystic areas, hemorrhagic foci. Higher T2 signal. Hormonal spectrum is wide — may produce estrogen and/or androgen. May be confused with malignancy due to younger age group.
Distinguishing Feature
Fibroma is markedly T2 hypointense (similar/lower than skeletal muscle), hormonally inactive (no endometrial thickening), and enhancement is weaker. Thecoma is slightly more T2 hyperintense, may cause endometrial thickening by producing estrogen, and enhances slightly better.
Distinguishing Feature
Granulosa cell tumor shows solid-cystic mixed structure, marked T2 hyperintensity, intense enhancement, and elevated inhibin. Thecoma is entirely solid with intermediate T2 signal and poor-to-moderate enhancement. Both may produce estrogen.
Distinguishing Feature
Sex cord-stromal tumor is a broad category. Thecoma is a specific member of this group. In general, sex cord-stromal tumors can be solid or mixed, hormonally active or inactive — specific subtype differentiation requires histopathological evaluation.
Urgency
routineManagement
surgicalBiopsy
Not NeededFollow-up
6-monthThecoma is a benign tumor. Surgical excision (oophorectomy or cystectomy) is the standard treatment. Hormonal symptoms (postmenopausal bleeding, endometrial thickening) completely resolve after surgery. Endometrial biopsy is recommended in patients with accompanying endometrial hyperplasia (to exclude endometrial carcinoma — risk of prolonged estrogen exposure). Malignant transformation (malignant thecoma) is extremely rare. Postoperative follow-up monitors estrogen levels and endometrial thickness.
Ovarian thecoma is a benign tumor but may be associated with endometrial hyperplasia and endometrial cancer due to estrogenic effects. Should be considered in patients presenting with postmenopausal bleeding. Surgical excision is curative.