Hibernoma
Definition
- Tumor of cells with features of brown fat
Diagnostic Criteria
- Circumscribed, lobulated mass
- Grossly yellow-brown
- Cellular features of brown fat
- Numerous small cytoplasmic vacuoles
- Pale to intensely eosinophilic granular cytoplasm
- Normal fat cells may be admixed
- 7% of cases are predominantly mature fat
- Cytologically bland
- Small central nuclei
- Prominent nucleoli
- Mitotic figures and cytologic atypia rare
- No clinical significance if present
- Small central nuclei
- May have myxoid stroma (9% of cases)
- Rarely combined with spindle cell lipoma
- Same clinical features and distribution as usual spindle cell lipoma
- Malignant neoplasms with brown fat differentiation are controversial
- May represent pleomorphic or myxoid liposarcoma
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342
Original posting : July 29, 2007
Updates: May 25, 2009
