Pure hibernoma of the breast: insights about its origins

Hibernomas are rare benign tumors composed of cells reminiscent of brown adipose tissue. In the mammary gland, hibernomas are extraordinary rare, with only 4 cases reported previously. We report the fifth case in a 37-year-old woman who presented with a slowly growing mobile mass in her right breast. A 2.2 cm well-circumscribed lobulated mass was completely removed. The histopathologic analysis showed the full characteristics of the hibernoma. A review of the clinicopathologic features of hibernomas, its relation to brown adipose tissue in humans, and considerations about its histogenesis are made.