Diagnostic challenges of a decidualized ovarian endometrioma mimicking a malignant tumor during pregnancy: the role of contrast-enhanced magnetic resonance imaging: a clinical case

Decidualized endometriomas in pregnancy are a rare finding and pose a significant diagnostic challenge as they mimic malignant ovarian neoplasms. We describe a clinical case of a 27-year-old patient at 15 weeks of gestation with a solid-cystic mass of the left ovary detected on ultrasound. MRI of the pelvis with intravenous contrast enhancement with gadobutrol (Gadovist) and DWI was performed for differential diagnosis. MRI revealed a mass consistent with an endometrioma with an intraluminal solid nodule (height <11 mm) that showed moderate heterogeneous contrast enhancement. A critically important feature was the absence of significant diffusion restriction: the ADC value of the node was 1.5–1.8×10^–3 mm²/s. There were no signs of invasive growth, lymphadenopathy, or carcinomatosis.

CONCLUSION: Comprehensive MRI evaluation, including analysis of morphology (nodule height), contrast enhancement kinetics, and especially quantitative ADC values, is a highly informative method for the differential diagnosis of decidualized endometrioma and malignant ovarian tumors in pregnant patients, justifying the choice of conservative tactics and avoiding unjustified surgical intervention.

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