Giant post-traumatic liponecrotic granuloma of the gluteal region: A case report with multimodality imaging findings.

Post-traumatic liponecrotic granuloma is a benign soft-tissue lesion resulting from adipose tissue necrosis after blunt trauma. Although post-traumatic fat necrosis is a recognized entity, large encapsulated lesions with a pseudotumoral appearance are rare and may closely mimic soft-tissue neoplasms, creating a diagnostic challenge. In this setting, multimodality imaging is essential for accurate lesion characterization and appropriate patient management. We report the case of a 40-year-old woman presenting with a progressively enlarging left gluteal mass that developed over 5 years following a road traffic accident. Clinical examination revealed a well-defined, firm, painless mass without overlying inflammatory skin changes. Ultrasound demonstrated a large avascular subcutaneous lesion measuring 122 × 109 × 89 mm (craniocaudal × anteroposterior × transverse). Computed tomography showed a well-circumscribed lobulated fat-containing mass with internal calcifications. Magnetic resonance imaging demonstrated a well-defined lobulated subcutaneous lesion with a thin hypointense capsule enclosing a central fatty component that was hyperintense on T1- and T2-weighted images, completely suppressed on fat-saturated sequences, and showed no significant postcontrast enhancement. The combination of a history of trauma and characteristic multimodality imaging findings strongly supported the presumptive diagnosis of post-traumatic liponecrotic granuloma. This case highlights the importance of correlating clinical history with ultrasound, computed tomography, and magnetic resonance imaging to accurately characterize chronic post-traumatic soft-tissue lesions. It also illustrates the diagnostic challenge posed by large encapsulated fat necrosis with a pseudotumoral appearance and emphasizes the value of multimodality imaging in establishing a confident presumptive diagnosis while potentially avoiding unnecessary invasive procedures.