SMN1 and leiomyoma: Schwannoma is more prone to focal bleeding, necrosis, and cystic degeneration, and the nearby nerves at both ends show a specific manifestation of “rat tail sign” on ultrasonography for identification.[14] Leiomyomas are more common in middle-aged and elderly patients, arise in the pelvis, retroperitoneal and abdominal cavity.[15] The morphology under the microscope is similar to that of IMT, however immunohistochemical expression of myogenic antibodies such as SMA is positive, and negative ALK can be distinguished from IMT.