Uterine myxoid leiomyosarcoma initially showing low signal intensity on T2 weighted images: A case report.

In the few articles describing MRI findings of myxoid leiomyosarcoma (MLMS), high signal intensity (SI) on T2-weighted images (T2WI) due to myxoid change was believed to be one of the common features. However, we encountered an MLMS with low SI similar to uterine myometrium on T2WI that subsequently grew with extremely edematous change even after 3 cycles of gonadotropin-releasing hormone agonist (GnRHa) treatment. Here we present this atypical MLMS case with radiologic-pathologic correlation. The patient was a 46-year-old woman with a chief complaint of low abdominal pain. The tumor was a pedunculated mass arising from the right anterior wall of the uterus that included a low-SI tumor-like component that partially transitioned into a peripheral high-SI component on T2WI and was diagnosed as hydropic leiomyoma. After 3 cycles of GnRHa therapy, the tumor size increased along with the size of the peripheral high-SI component on T2WI, while the size of the low-SI tumor-like component decreased. A small markedly low-SI area on both T1 and T2WI and a subtle high-SI area on fat-saturated T1WI indicating hemorrhage were present within the tumor. Pathologically, not only the peripheral high-SI component but also the low-SI tumor-like component on T2WI corresponded to MLMS, and the high-SI component was associated mainly with edematous change rather than myxoid change. MLMS may initially show low SI on T2WI and change to high SI mainly due to edematous change with rapid growth. Intratumoral hemorrhage might be the only key feature to differentiates MLMS from hydropic leiomyoma.