Intramuscular Hibernoma of the Scapular Region Misdiagnosed on Cytology as a Malignant Lesion: A Report of a Rare Case

Hibernomas are extremely rare benign tumors of adipose tissue characterized by an admixture of brown fat cells with granular, multivacuolated cytoplasm and white fat cells. Hibernomas account for 1.6% of benign adipose tissue tumors and approximately 1.1% of all adipocytic tumors. Around 10% of these cases are intramuscular. It was initially described in the early 1900s as being composed of brown fat. Hibernomas usually occur in third to fourth decades of life and the most frequent sites being thigh, trunk, shoulder, back etc. Cytological differential diagnoses of hibernoma include well differentiated liposarcoma, myxoid/round cell liposarcoma, chondroid lipoma and benign granular cell tumor.  Due to its abundant vascularity evident on angiography, it can sometimes mimic a malignant lesion, from which it needs to be distinguished as complete surgical excision is the only treatment required for a hibernoma. Moreover, it has no malignant or metastatic potential. We presented a rare case of intramuscular hibernoma of the scapular region in a 34-year-old male, in which cytology was reported as pleomorphic fibrolipomatous malignant lesion.