Adenomatoid tumors of the uterus: magnetic resonance imaging features with clinical and histopathologic correlation.

Purpose: Adenomatoid tumor (AT) of the uterus is a rare benign neoplasm of mesothelial origin. To date, few studies have reported the magnetic resonance imaging (MRI) findings and clinicopathologic features of uterine ATs. This study aimed to summarize the MRI features of uterine ATs and relate them to their clinicopathologic findings, with the goal of improving the accuracy of preoperative diagnosis. Methods: Sixteen surgically resected, histopathologically confirmed uterine ATs were retrospectively reviewed. Clinical data, imaging characteristics, and histopathologic findings were systematically analyzed. Results: The 16 patients had a median age of 51 years. ATs coexisted with uterine fibroids in 8 of the 16 patients. Among the 16 patients, 15 each had a single AT, and one patient had two synchronous ATs, for a total of 17 lesions. Seven lesions were intramural, and 10 were subserosal. All 17 lesions were oval, with a maximum diameter of 9-65 mm; four had ill-defined margins and 13 had well-defined margins; no identifiable capsule was seen. Thirteen lesions were solid, two were cystic-solid, and two were cystic. The solid components were isointense on T1-weighted imaging (T1WI) and predominantly hypointense on T2-weighted imaging (T2WI). Small foci of cystic degeneration were present in five lesions, and four exhibited a "target sign" (central hypointensity with a peripheral annular hyperintense rim) on T2WI. Solid components demonstrated mild diffusion restriction in most lesions. The solid components demonstrated moderate-to-marked enhancement, comparable to or slightly less than that of the adjacent myometrium. The cystic components were hypointense on T1WI and hyperintense on T2WI without enhancement. Two cystic lesions with septa, both showed peripheral enhancement and progressive enhancement of the internal septa. Imaging findings correlated closely with histopathologic findings. The tumors consisted of gland-like spaces of varying sizes interspersed with smooth muscle and fibrous tissue. Differences in the relative proportions of these components accounted for the diverse imaging appearances. Conclusions: Uterine ATs predominantly present as solid masses without an identifiable capsule. Small foci of cystic degeneration or a "target sign" on T2WI, observed in a subset of cases, may represent nonspecific imaging findings of uterine ATs. However, definitive diagnosis still requires histopathologic examination.