What does a high T2 signal on MRI indicate in an adnexal mass?

High T2 Signal in an Adnexal Mass: Interpretation

A high T2 signal in an adnexal mass is most commonly associated with fluid-containing benign lesions, but the specific diagnosis depends on additional MRI characteristics and clinical context.

What High T2 Signal Indicates

High T2 signal (hyperintensity) on MRI reflects high water content within a lesion. In adnexal masses, this finding has different implications depending on the mass composition:

Benign Entities with High T2 Signal

Cystic/Fluid-Containing Lesions:

• Simple cysts - uniformly high T2 signal, no solid components 1
• Hydrosalpinx - tubular cystic structure with high T2 signal 1
• Peritoneal inclusion cysts - high T2 signal conforming to pelvic spaces 1
• Tubo-ovarian abscess (TOA) - variable signal from low to intermediate or high T2 signal, with thick irregular walls 2

Specific Benign Diagnoses:

• Endometriomas - typically show low T2 signal (not high), which is an important distinguishing feature 1
• Fibromas - characteristically show low T2 signal with enhancement 1

Malignant Lesions with High T2 Signal

Solid tissue that is T2 hyperintense within an adnexal mass raises concern for malignancy 3. Specifically:

• Papillary projections with high T2 signal in malignant masses 3
• Mucinous carcinomas - can demonstrate high T2 signal
• Solid components with T2 hyperintensity are more common in malignant than benign O-RADS MRI 4 lesions (p ≤ 0.03) 3

Critical Distinguishing Features

To differentiate benign from malignant causes, evaluate:

1. Enhancement pattern - Vascular vegetations and enhancing solid tissue are the best indicators of malignancy 1
2. Solid tissue characteristics - Size and T2 signal intensity of solid components help stratify risk 3
3. Associated findings - Ascites strongly suggests malignancy 1
4. Diffusion-weighted imaging (DWI) - Malignant solid tissue typically shows restricted diffusion with lower ADC values 2

Diagnostic Approach

When encountering high T2 signal in an adnexal mass:

• If the mass is uniformly cystic with high T2 signal and no solid components → likely benign (simple cyst, hydrosalpinx)
• If there are solid components with high T2 signal → requires contrast-enhanced MRI to assess for enhancement, which significantly increases malignancy probability 1
• Contrast-enhanced MRI is superior to non-contrast MRI for characterizing indeterminate masses, with posttest probability of malignancy reaching 80% in premenopausal and 95% in postmenopausal women 1

Common Pitfall

Do not assume a T2 hyperintense rim sign indicates a benign pedunculated leiomyoma. While up to 23% of uterine leiomyomas show a high T2 signal rim (best seen on T2 fat-saturated sequences), up to 40% of ovarian fibromas can also demonstrate this finding 4. Therefore, a solid adnexal mass with a T2 rim sign cannot be assumed benign without further characterization.

The key takeaway: High T2 signal alone is non-specific. The presence and characteristics of solid tissue, enhancement patterns, and DWI findings are essential for accurate risk stratification.