Clear cell carcinoma of the ovary: comparison of MR findings of histological subtypes

PURPOSE: To retrospectively compare the MR findings of histological subtypes of clear cell carcinomas (CCCs) of the ovary. MATERIALS AND METHODS: This single-center retrospective study was approved by the institutional review board, and the requirement for informed consent was waived. Between April 2005 and August 2015, we found 51 consecutive patients with histopathologically proven CCCs. Among them, 44 CCCs in 37 patients who underwent preoperative MR imaging were included. CCCs were pathologically divided into three subgroups: (1) four clear cell adenofibroma-associated CCCs, (2) 21 endometriosis-associated CCCs, and (3) 19 indeterminate CCCs. The statistical tests were used to compare the frequency of qualitative assessments and value of quantitative measurements among the histological subtypes. RESULTS: On T2-weighted images, hypointense areas within solid components were more frequently observed in clear cell adenofibroma-associated CCCs [3/4 (75%)] than in the remaining CCCs [1/40 (3%)] (p < 0.01), and the signal intensity ratios (SIRs) of solid components were significantly lower in clear cell adenofibroma-associated CCCs (0.27 ± 0.13) than in the remaining CCCs (0.61 ± 0.18) (p < 0.01). On T1-weighted images, hyperintensities of cystic components were more frequently observed in the endometriosis-associated CCCs [17/21 (81%)] than in the remaining CCCs [5/20 (25%)] (p < 0.01), and the SIRs of cystic components were significantly higher in endometriosis-associated CCCs (2.99 ± 1.51) than in the remaining CCCs (1.82 ± 1.10) (p < 0.01). CONCLUSION: MR features may help differentiate between adenofibroma-associated and endometriosis-associated CCC.