Assessment of endometrial cancer with microcystic, elongated, and fragmented pattern invasion using multiparametric MRI.

Objective: To assess the MRI findings of endometrial cancer with microcystic, elongated, and fragmented (MELF) pattern invasion and to evaluate the optimal sequences to detect deep myometrial invasion with MELF.

Methods: This retrospective single-center case-control study included 85 patients with endometrial cancer, including 17 patients with MELF, between December 2020 and January 2023. Preoperative MRI, including T2-weighted imaging (T2WI), diffusion-weighted imaging (DWI), and dynamic contrast-enhanced (DCE) with equilibrium phase contrast-enhanced (CE) MRI were reviewed by three radiologists. DWI signal gradation with DWI-CE mismatch (DG-DCM) and tumor-myometrium synchronous early enhancement (TME) were evaluated, as well as the diagnostic performance for deep myometrial invasion, first with T2WI + CE alone and then with the addition of DWI + DCE. Pathology was used as the reference standard.

Results: The sensitivity and specificity of DG-DCM were 41.2-76.5% and 89.7-98.5%, and those of TME were 70.7-82.4% and 94.1-95.6%, respectively, for MELF by the three readers. For the diagnosis of deep myometrial invasion with MELF, the addition of DWI + DCE to T2WI + CE significantly improved the sensitivity for two readers (from 16.7 to 91.7% for Reader 1, from 16.7 to 83.3% for Reader 2, p < 0.01) and the accuracy for one reader (from 35.3 to 82.4% for Reader 1, p < 0.01). In contrast, sensitivity, specificity and accuracy did not change with the addition of DWI + DCE in tumors without MELF.

Conclusions: Endometrial cancer with MELF may show characteristic MRI findings of DG-DCM and TME. The value of DWI and DCE in detecting deep myometrial invasion may be high for MELF pattern invasion.