Decidualized endometrioma during pregnancy: recognizing an imaging mimic of ovarian malignancy.

OBJECTIVE

To present the ultrasound and magnetic resonance imaging findings that may allow for a prospective diagnosis and expectant management of decidualized endometriomas because the rare occurrence of decidualization in the ectopic endometrial stroma of an endometrioma during pregnancy can mimic ovarian cancer at imaging.

CASE REPORT: Smooth lobulated mural nodules with prominent internal vascularity were noted in an apparent right ovarian endometrioma on serial ultrasound studies in a 34-year-old woman at 12, 21, 27, and 30 weeks of gestation. Magnetic resonance imaging demonstrated the nodules to be strikingly similar in intensity and texture to the decidualized endometrium in the uterus on T2-weighted sequences. A provisional diagnosis of decidualized endometrioma allowed for expectant management with immediate postpartum resection and confirmation of the diagnosis.

CONCLUSIONS

Decidualized endometrioma can mimic ovarian malignancy during pregnancy, but a prospective diagnosis may be possible when solid smoothly lobulated nodules with prominent internal vascularity within an endometrioma are seen from early in pregnancy, and the nodules demonstrate marked similarity in signal intensity and texture with the decidualized endometrium in the uterus at magnetic resonance imaging.