Intraosseous hibernoma in the rib

A 64-year-old man was admitted with paroxysmal left-side thoracic pain. CT scan showed an irregular appearance, expansile, osteolytic lesion of the left seventh rib. Wide en bloc excision of the tumour was performed. Macroscopic examination showed that a 3.5 cm × 3.0 cm × 3.0 cm solid lesion with destruction of bone. Histological examination showed that the tumour cells were arranged in plate shaped and interspersed between the bone trabeculae. Mature adipocytes were noted in the tumour tissues. The immunohistochemical stainings showed that the vacuolated cells were positive for S-100 protein and negative for CD68 and CD34. These clinicopathological features were consistent with intraosseous hibernoma.