To evaluate the efficacy of morphological features and signal intensity in the differentiation of benign, malignant ovarian lesions, and metastasis by MRI.

A total of 117 patients (age range 24-88) underwent pelvic MRI, of which 38 had benign, 56 had malignant ovarian lesions, and 23 had metastasis, respectively. All lesions were pathologically confirmed. T1, T2WI, and T2WI-FS were obtained, and the morphological features and quantitative/qualitative signal characteristics on T1WI and T2WI were analyzed in the lesions.

The differentiation between benign and malignant ovarian lesions showed that bilaterality, a larger size, a larger size of the individual solid component, irregular shape, cystic-solid structure, more than 3 irregular thickening of internal septa, multilocular cyst, implants, and ascites were significantly more typical for malignant lesions (p<0.001, 0.005, 0.003). However, in differentiating between malignant lesions and metastasis, a larger size of the individual cyst component, more than 3 irregular thickening of internal septa, thickening of the cyst wall, and implants were significantly more typical for malignant lesions (p<0.012, 0.02, 0.009). The cystic component was present in 47.6% (10/21) of benign lesions (excluding endometroid cysts and teratoma) and 90.4% (57/63) of malignant lesions. There were no differences in T1WI and T2WI signal characteristics in the cystic component between benign and malignant lesions. However, when we included endometroid cysts and teratoma in the group of benign lesions (18 cases), we found a statistically significant difference (p=0.03) between benign and malignant ovarian lesions on T1WI because endometroid cysts and teratoma had a higher signal intensity on T1WI compared to the cystic component of malignant lesions. The solid component was present in 71.4% (15/21) of benign and 98.4% (62/63) of malignant lesions. Significant differences in T2WI signal characteristics (p=0.001) in the solid components were found between benign and malignant lesions. A higher signal intensity of the solid component on T2WI was more specific for malignant lesions than for benign. There were no differences in T1WI signal characteristics in the solid component between benign and malignant lesions. Also, we did not find a significant difference in T1/T2WI signal characteristics in the solid components between malignant lesions and metastasis. According to the ROC analysis, the SI of the solid component equal to 0.94 can be used as a threshold for differentiating between benign and malignant ovarian lesions (sensitivity 91%, specificity 80%, PPV 95%, and NPV 70%).

Conclusion: Described MRI signs are useful for the differential diagnosis of benign, malignant ovarian lesions and metastasis. However, the combination of DWI/ADC and DCE with conventional MRI may be effective in differentiating ovarian lesions.