Case report: MR appearance of hemangiopericytoma of the thigh.

We report a case of hemangiopericytoma in the thigh of a 42-year-old woman. CT examination depicted a peripherally enhanced, multicystic mass without calcification. On T1-weighted images of MRI, the mass showed slightly high signal intensity relative to muscle, with the exception of the lower pole, which showed high signal intensity. On T2*-weighted images, the mass showed high signal intensity and cystic appearance. The lower pole showed low signal intensity on T2*-weighted images and was thought to be intratumoral hemorrhage. Low signal intensity structures on both T1- and T2*-weighted images were observed within and around the mass. They were thought to be dilated vessels, although this was not confirmed at surgery. Hemangiopericytoma should be considered in the differential diagnosis of a tumor in the thigh when MR images show the mass with slightly high signal intensity on T1-weighted images, intratumoral hemorrhage, and flow voids within or adjacent to the tumor.