MRI of endometriotic cysts in association with ovarian carcinoma.

OBJECTIVE: Although mural nodules are considered to be the most important hallmark in the recognition of ovarian cancers accompanied with endometriotic cysts, benign neoplasms and even inflammatory diseases can show similar MRI findings. We sought to clarify the MRI characteristics of malignancy accompanied with endometriotic cysts of the ovary.

MATERIALS AND METHODS: Contrast-enhanced MRI was performed and endometriosis was pathologically confirmed in 49 patients with endometriotic cysts displaying mural nodules. Malignancy was pathologically diagnosed in 33 patients and benignity, in 16. Clinical data including patient age and MRI findings in terms of the size of the endometriotic cysts, number of loculi, presence of shading of the cysts, size of the mural nodules, signal intensity of the mural nodules on T1- and T2-weighted images, and contrast enhancement of the mural nodules were retrospectively reviewed. Statistical analysis of each parameter used the Mann-Whitney U test.

RESULTS: The mean age of the patients and mean size of the endometriotic cysts were significantly higher in patients with a malignant condition than in those with a benign condition. Contrast enhancement of the mural nodules was observed in 97% of malignant and 44% of benign tumors. The size of the mural nodules was significantly larger in patients with a malignant condition than in those with a benign condition. Differences in size between the bilateral diseases, multilocularity, existence of shading, and the signal intensities of mural nodules were not significantly different between the malignant and benign conditions.

CONCLUSION: Endometriotic cysts with enhanced mural nodules are not always complicated with malignancy. In elderly patients, the presence of large enhanced nodules on large endometriotic cysts is more likely to indicate malignancy.