Presentation
Right gluteal region mass since birth with a large cutaneous lesion suggestive of giant congenital nevus.
Patient Data
The MRI sequences demonstrate a large well-circumscribed lobulated soft tissue mass arising from the gluteus maximus muscle. It is isointense to striated muscle on T1WI and shows inhomogeneous high signal on T2WI. It contains foci of hemorrhage with hematocrit effect, wherein the nondependent plasma appears hypointense on T1WI and hypointense on T2WI, whereas the RBC sediment (hematocrit) appears hypointense on both sequences. The mass enhances intensely post-contrast.
Case Discussion
The infant went on to have complete resection of the tumor. The histopathological exam and immunohistochemistry were consistent with a malignant peripheral nerve sheath tumor (MPNST) on a pre-existing giant congenital nevus.