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

Objectives: 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.

Materials and 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.

Conclusion: 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.