Solid non-invasive ovarian masses on MR: Histopathology and a diagnostic approach

Abstract

Purpose The purpose is to clarify the histopathology of the solid, non-invasive ovarian masses and to investigate the MR characteristics that distinguish benign from malignant. Materials and methods From 1996 to 2008, we identified 38 cases with predominantly solid non-invasive ovarian masses examined by contrast MR. We evaluated the signal intensity on T2WI and degree of contrast enhancement. In 31 of these cases with dynamic contrast study, we classified the enhancing patterns of the masses into gradually increasing and plateau after rapid increase patterns. Result Sixteen cases were benign sex-cord stromal tumors, three were other types of benign tumors, nine cases were diagnosed with primary malignant ovarian tumors, and 10 showed metastatic tumors. Low intensity on T2WI was observed in 15 benign and 2 malignant tumors. The gradually increasing pattern was observed in all 17 benignancies and 5 of the 14 malignancies. In the equilibrium phase, the masses were weakly enhanced in all 19 benignancies and only 4 of 19 malignancies. The diagnostic criteria, that low signal intensity masses with gradual weak enhancement are benign showed 93.3% accuracy and 100% positive predictive value. Conclusion Benign solid ovarian masses tended to show low signal intensity on T2WI and gradual weak enhancement.