Cut section of the resected specimen showing a well-demarcated tumor adjacent to the submandibular gland. Hibernoma consisting mainly of multivacuolated cells with small round nuclei and adult adipocytes. Mitoses and pleomorphism were absent. A rich vascular network was found. The histological features were considered to be those of a hibernoma.
Some tumor cells contain vacuoles indenting the nucleus.
The mitochondrial matrix was of medium to high density and showed large and abundant dense granules. The endoplasmic reticulum was very scarce and the Golgi apparatus inconspicuous. The nuclei were round and contained uniformly distributed chromatin condensed under nuclear membrane. In some cells, multiple intracytoplasmic lipid droplets caused scalloping of the centrally situated nucleus. Hibernoma cells were surrounded by a well-defined basal lamina.