Hibernoma (brown lipoma): causes, symptoms, diagnosis, treatment

Hibernoma (syn: brown lipoma, granular cell tumor of adipose tissue, lipoma from lipoblast) develops from lipochrom-rich brown adipose tissue, a cup in middle-aged and elderly women, in locations of brown fat in the form of rudimentary remains (along the spine, on the neck, to the axillary cavities, inguinal, lumbar and gluteal regions). The cases of the appearance of this tumor in children are described. Clinically it is a subcutaneous solitary tumor, protrude above the surface of the skin, with a diameter of 3 to 12 cm, a plastic consistency.

Pathomorphology of the hibernoma (brown lipoma). The tumor is encapsulated and divided by connective tissue layers into separate lobules, which are very vascularized. Most of the cells that make up the tumor are multivacuolar with a granular eosinophilic cytoplasm between the vacuoles and small, centrally located nuclei. Their diameter varies from 20 to 55 microns. Among them there are intermediate forms - the transition from multivacuolar cells to large, monovacular. They have a nucleus located on the periphery of the cell, with sizes up to 120 microns. In some lobules, especially on the periphery of the tumor, only monovacular cells can be located. Vacuoles in multivacuolar and monovacular cells are colored with Sudan III in orange. In addition, there are cells of the third type, which do not contain fat, have a fine-grained eosinophilic cytoplasm. They are smaller than multivacuolar cells, they have a diameter of about 12 microns.

Histogenesis of the Hibernoma (brown lipoma). The tumor develops from cells located in the locations of brown fat. Although in their development all fat cells pass through the stages of multivacuolar and monovacuolar cells, they differ from each other in electron microscopy. Cells of brown fat, as well as cells of the hibernoma. Contain large mitochondria with a complex internal structure and a large number of transversely located tubular cristae, while ordinary fat cells contain small mitochondria with a weak internal structure. Some authors believe that the granularity of cytoplasm of brown fat cells is associated with the presence of large mitochondria. The cause of differentiation of the clone of brown fat cells, according to O.R. Nörnstein and F. Wcidner (1979), is an enzyme defect. Brown coloration is caused, in their opinion, by products of oxidation of phospholipids.

[1], [2], [3], [4]