Hibernoma: a possible model of brown fat histogenesis.

Hibernomas are composed of cells remarkably similar to those observed in brown adipose tissue. A surgically resected hibernoma was observed to contain cells at all stages of maturation from immature, relatively lipid free cells to multiloculated and finally uniloculated adipocytes. The ultrastructural features of adipocytes contained in the hibernoma were compared to previously reported features of differentiating preadipocytes and lipid depleted mature adipocytes derived from human white adipose tissue. This comparison confirmed the existence of distinct mitochondrial and cytoplasmic membrane component differences at all developmental stages and suggests that brown and white adipose tissue are two unique histologic types.