A giant intramuscular myolipoma of the gluteus maximus mimicking well-differentiated liposarcoma: a diagnostic challenge.

Myolipoma is an exceptionally rare benign mesenchymal neoplasm composed of mature adipose tissue admixed with smooth muscle elements. We report a 67-year-old male who presented with a 3-month history of a progressive, painless mass in the right gluteal region. Ultrasound and magnetic resonance imaging revealed a large (125 × 88 × 60 mm) encapsulated intramuscular mass with thick enhancing septations and restricted diffusion, raising high suspicion for well-differentiated liposarcoma. Two sequential ultrasound-guided core needle biopsies were non-diagnostic. Complete surgical excision was performed; intraoperative findings demonstrated a well-encapsulated lesion with no invasion of surrounding structures. Definitive histopathology confirmed a benign intramuscular myolipoma. This case underscores that large deep-seated myolipomas can radiologically mimic liposarcoma, that percutaneous biopsy may be non-representative, and that surgical excision remains both the definitive diagnostic and therapeutic gold standard.