Pleomorphic hyalinizing angiectatic tumor of soft tissue in the distal thigh: A case report and literature review

Pleomorphic hyalinizing angiectatic tumor of soft tissue (PHAT) is a rare, low-grade neoplasm of uncertain lineage that predominantly affects the lower limbs of middle-aged adults. We report the case of a male in his early 20s who presented with a progressively enlarging, mildly tender mass above the right knee, present for 6 years. Imaging studies revealed a well-circumscribed lesion with obvious contrast enhancement on magnetic resonance imaging and marked internal vascularity on color Doppler ultrasound, located anterior to the distal quadriceps femoris. Extended excision was performed, and histopathologic examination confirmed the diagnosis of pleomorphic hyalinizing angiectatic tumor of soft tissue with negative surgical margins (R0 resection). The patient remained disease-free at the short-term follow-up (as of mid-2025). This report highlights the clinicopathologic features that differentiate pleomorphic hyalinizing angiectatic tumor of soft tissue from mimics such as myofibroma and intramuscular hemangioma, particularly in younger patients and at unusual anatomical locations.