A case report of lipoma-like hibernoma in axilla: A rarely benign tumor of brown adipose tissue

Background: Hibernoma or lipoma of brown fat is a rare benign tumor, representing 1.6% of the neoplasms of this tissue. Because of its histological characteristics can be wrongly classified as liposarcoma, therefore a correct differential diagnosis is necessary to provide appropriate treatment.Case presentation: The patient on which this case study is based is a 44-year-old male with a painless soft mass in his axilla located by his 4th and 5th ribs. The resected specimen did not have the classic macroscopic features of lipoma or fibrolipoma. Microscopically, the report described a proliferation of unilocular adipocytes with eccentric nucleus and, in less frequency, multilocular adipocytes with central nucleus. He had no recurrence after excision.Conclusions: Despite radiology studies and other technologies such as magnetic resonance imaging, computerized axial tomography (CAT), etc., the clinical diagnosis of hibernoma could be difficult. Lipoma-like hibernoma only have a few multilocular cells and can be wrongly classified as liposarcoma. Well-differentiated liposarcoma resembles it on low-power examination. Due to this it is especially important to perform a differential diagnosis with lipoma, fibroma, and even with liposarcoma. In this study we describe the histological features, the molecular markers and cytogenetic aspects that contribute to differentiate hibernoma from others tumors.