A 34-year-old woman with suspected endometriosis undergoes pelvic MRI prior to laparoscopy. A 4 cm unilocular right adnexal cyst is identified. Which MRI finding is the MOST specific for diagnosing an endometrioma?

• A Rim enhancement on post-gadolinium T1-weighted images
• B T1 hypointensity with T2 hyperintensity
• C Diffusion restriction on DWI with low ADC values
• D T1 hyperintensity with T2 hypointensity (T2 shading sign) ✓

Explanation

The T2 shading sign, where an endometrioma shows T1 hyperintensity (due to blood products) with corresponding T2 hypointensity (due to concentrated iron and protein from repeated haemorrhage), is the most specific MRI criterion for endometrioma. Simple haemorrhagic cysts may show T1 hyperintensity but lack the characteristic T2 shading. Rim enhancement suggests a neoplasm. Diffusion restriction is nonspecific and seen in many cystic lesions including malignancies.

Reference: Diagnostic Imaging: Gynecology (Osborn), 2nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.