Lipomatous lesions of the thyroid gland: a review.

Described are rare thyroid lesions which either contain mature adipocytes or consist of lipid-rich follicle cells. Of the former, diffuse lipomatosis and adenolipoma of the thyroid are most likely to be derived from heterotopic islands of fat cells included in the gland during embryogenesis. On the other hand, metaplastic origin of fat cells from stromal fibroblasts due to chronic tissue hypoxia is presumed responsible for the presence of fatty tissue in amyloid goiters. Massive steatosis of follicle cells, as seen in the lipid-rich variant of clear cell thyroid adenomas and carcinomas, is, however, claimed to most likely result from metaplastic transformation of neoplastic thyrocytes. Pathomorphological and clinical features of the aforementioned lesions are discussed.