Endometrioid adenocarcinoma of the ovary: MRI findings with emphasis on diffusion-weighted imaging for the differentiation of ovarian tumors

Background: Preoperative differentiation of ovarian malignant tumors still remains a challenge. Diffusion-weighted imaging (DWI) provides information about cellularity of the lesion and might facilitate discrimination between different malignant ovarian lesions. Purpose: To evaluate magnetic resonance imaging (MRI) findings of endometrioid adenocarcinoma of the ovary and to determine the value of DWI in the differential diagnosis of malignant and benign adnexal tumors. Material and Methods: The following MRI findings were reviewed in 162 patients (21 endometrioid adenocarcinoma, 103 other malignant tumors, 38 benign tumors): lesion size, morphological appearance, T2-weighted (T2W) signal intensity, T1-weighted (T1W) signal intensity, contrast-enhancement pattern, DWI signals with apparent diffusion coefficient (ADC) calculated for b800 s/mm2 in solid tumor components. Results: The most common morphological appearance was predominantly cystic lesion, found in 90.3% of patients with endometriod adenocarcinoma. The solid parts were slightly hyperintense on T2W images in 19 patients with marked enhancement after contrast administration. No significant difference (P0.13) in conventional MRI features was found between endometrioid adenocarcinoma and other malignant ovarian tumors. Hyperintensity on DWI was more frequently observed in malignant tumors than in benign lesions (P<0.001). ADC values were significantly lower in endometrioid adenocarcinoma than other malignant tumors (0.79=0.21 vs. 0.90=0.19; P0.04) and in all malignant lesions compared with benign tumors (0.88=0.31 vs. 1.33=0.17; P<0.001). Conclusion: DWI with ADC measurement could indicate the presence of endometrioid adenocarcinomas due to a slightly but significantly lower ADC values compared to other malignant ovarian lesions. Thus, DWI is beneficial and should be part of a standard protocol for the evaluation of indeterminate adnexal lesions.