Useful preoperative examination findings to classify the grade of ovarian primary mucinous tumor.

To evaluate various imaging features on magnetic resonance imaging (MRI) and tumor markers and their utility to assess various grades of ovarian primary mucinous tumors (OPMTs): benign, borderline, or malignant. Ninety-five pathologically diagnosed OPMTs [53 benign, 24 borderline malignant (BM), and 18 malignant] were selected in this retrospective study. MRI features of the ovarian mass, namely the maximum diameter, honeycomb loculi, solid components (SC), stained-glass pattern, and signal intensity of the cyst on T1- (T1WI) and T2-weighted imaging (T2WI) with/without fat suppression, and preoperative STMs, namely carcinoembryonic antigen (CEA), carbohydrate antigen (CA) 19-9, and CA125, were compared between the three tumor grades using univariate analysis. We also analyzed the findings to estimate the pathological diagnosis using classification tree (CT) analysis. Maximum diameter, honeycomb loculi, SC, stained-glass pattern, signal intensity of the cyst [hyperintensity on both T1WI and T2WI (T1-hyper/T2-hyper), and hyperintense on T1WI and hypointense on T2WI (T1-hyper/T2-hypo)], and CEA and CA 19-9 concentrations were significantly different between the three tumor grades (p < 0.05). The concordance rate with the pathological diagnosis was the highest with diagnosis by the CT comprising T1-hyper/T2-hypo, CEA, and CA 19-9 and by the CT comprising T1-hyper/T2-hypo, CEA, and SC. Four types of findings were important for OPMT grading. Lesions negative for both T1-hyper/T2-hypo and CEA suggest benign; lesions positive for T1-hyper/T2-hypo and negative for CA 19-9 or SC suggest BM; and lesions negative for T1-hyper/T2-hypo and positive for CEA, or positive for both T1-hyper/T2-hypo and CA 19-9 or SC suggest malignancy.