A case report of hibernoma in the thigh comprising the femoral neuromuscular bundle

INTRODUCTION: Hibernomas are rare, slow-growing, painless, benign tumors of soft tissue that develop from residual brown fat cell showing predilection for areas where brown fat is more common in fetuses and infants. Due to the rarity of the tumor its often overlooked or mistaken for other pathologies such as liposarcoma. CASE PRESENTATION: Using the CARE 2020 criteria we describe a 26-year-old man who presented with painful swelling of the thigh. A magnetic resonance imaging examination without contrast showed a mass in the medial thigh just lateral to the femoral artery. A biopsy specimen was obtained from his thigh for histopathological analysis, and the findings suggested a hibernoma. A wide resection was performed, and it showed that the femoral nerve was lateral to the mass, with the course of the nerve altered due to mass effect. The mass was sent for a histopathological examination, and the findings were consistent with a hibernoma. Two weeks post-operative, the patient reported a considerable decrease in pain intensity, and six months post-operative, he reported complete pain relief. DISCUSSION: Hibernomas are unusual tumors that are benign and usually painless, but the large size the tumor can reach and proximity to vital structures can explain the growing trends symptomatic nature of some hibernomas. A proper and step wise approach using clinical, radiological and histopathology is important to Diagnose and plan surgical management. Proper understanding of the proximity of adjacent structures and the high vascularity of the tumor. CONCLUSION: Because of the rarity and under reporting of hibernomas they are often misdiagnosed as large lipomas or malignant soft tissue tumors, underscoring the importance of histopathology in ensuring accurate diagnosis and anticipating intraoperative. Careful dissection and ligation of the vasculature with the understanding of adjacent anatomy are key to safe tumor excision.