Aggressive gluteal fibromatosis: a rare case associated with spontaneous superior gluteal artery pseudoaneurysm

Deep fibromatosis is a locally aggressive neoplasm commonly involving the extremities. Several authors have described imaging features and complications associated with deep fibromatosis. We present the case of a 33-year-old man who presented with a right gluteal fibrous mass identified on magnetic resonance imaging (MRI), which was associated with a pseudoaneurysm originating from the right superior gluteal artery on serial follow-up with MRI and computed tomography. No intervention was done, and after conservative management, spontaneous thrombosis of the pseudoaneurysm was developed. Such imaging finding is the first report of a spontaneous development of pseudoaneurysm caused by deep fibromatosis, which could be a life-threatening condition and should be considered when dealing with deep fibromatosis and deciding on the appropriate treatment.