Radiological reasoning: imaging characterization of bilateral adnexal masses

A 46-year-old woman presented with bilateral adnexal masses on pelvic sonography, a complex cystic mass on the right, and a homogeneously hypoechoic, solid-appearing mass on the left. Pelvic MRI showed a T1 hypointense, T2 hyperintense, nonenhancing mass in the right ovary and a homogeneously T1 hyperintense lesion with mixed T2 signal in the left ovary. Fat-saturated T1-weighted sequences showed the left ovarian lesion to be an endometrioma containing a high concentration of hemoglobin breakdown products and revealed other endometriotic implants in the right ovary, broad ligament, and cul-de-sac. Follow-up pelvic sonography 9 weeks later showed resolution of the right complex cystic ovarian mass, indicating that it was a physiologic hemorrhagic cyst.Imaging features of benign and malignant ovarian masses overlap. If imaging is inconclusive in characterizing an adnexal mass as benign, the mass will be resected rather than followed up because of the concern for a rapidly growing ovarian cancer. Thus, the goal of imaging is to identify unequivocally the benign lesions that can be left untreated. Pelvic MRI provides a powerful adjunct to pelvic sonography in characterizing adnexal masses as benign.