Lipoma-like hibernoma of the breast: A case report and literature review

Hibernomas are uncommon and benign tumors made up of brown fat cells. These tumors are typically found in the thigh, axillae, shoulder, back, neck, thorax, arm, and retroperitoneum. There are 4 histological variants of hibernomas, including the typical pattern, myxoid, lipoma-like, and spindle cell variant. The lipoma-like variant is characterized by numerous univacuolated adipocytic cells with intermingled multivacuolated granular cells. It is worth noting that lipoma-like hibernoma in the breast is infrequent. In this case, we present a 72-year-old woman with a history of moderately differentiated cholangiocarcinoma, obesity, and no family history of breast cancer. She consulted for a mass sensation in her right breast that had been present for a year. The mass was not painful and showed no inflammation or nipple discharge. Upon physical examination, a palpable 14 cm mass was identified, occupying the 2 internal quadrants and causing deformation of the surface of the right breast. Imaging studies indicated a solid mass in the lower-inner quadrant of the right breast, which was oval-shaped, well-defined, and displayed internal vascularization. Initially, a diagnosis of low-grade liposarcoma was considered, leading to a core needle biopsy guided by ultrasound. However, the histopathology study revealed a lipoma-like hibernoma, an exceedingly rare benign lesion. Lipoma-like hibernoma can present as a palpable mass or may be incidentally discovered. It should be considered in the differential diagnosis of any lesion containing fatty content. Imaging methods may suggest its presence, but histopathology confirms the diagnosis and its accuracy prevents needless overtreatment.