Hibernoma-A rare tumor on rare site

Hibernoma is a rare benign tumor that originates from brown fat. Hibernoma is thought to arise from areas containing residual brown fat like- the interscapular area, axilla, neck, chest, abdominal cavity, and retroperitoneum. The incidence of this rare tumor has very rarely been reported to occur over the forehead. Being a benign tumor, no association of malignant transformation or metastasis has been reported. A 23-year-old male presented with a complaint of a painless non-progressive swelling over the forehead for the past 6 months. On examination, the swelling was 2x2 cm, soft, mobile, non-tender, and non-pulsatile with no skin changes. FNAC did which shows sheets and clusters of adipocytes with abundant foamy cytoplasm and reported as “Hibernoma”. The patient has been asked to follow up and for the last 1 year, the tumor is still non-progressive with no pressure symptoms and hence has not undergone surgery. Hibernoma is a rare benign tumor of brown fat tissue which constitutes only 1.6% of benign lipomatous tumors but their actual prevalence is still unknown. This tumor very rarely may occur in the forehead area although incidence over the forehead has rarely been reported. Since this tumor is slow growing, painless non-progressive; it mostly presents as an asymptomatic tumor. It has to be included in the differential diagnosis of adipocyte-containing tumors to prevent false treatment.