[Proliferation of fat cells in lipomas]

Common lipomas and destructive ones (intramuscular, infiltrating, necrotizing and destroying surrounding tissues) were studied in 9 patients electron-microscopically and radioautographically. The adequacy of necrotizing processes and regeneration was observed: normal fat tissue-lipoma-destructive lipoma. In the latter besides pronounced destruction of tissue (adipocytes, vessels, muscles at the border with tumour), there was accelerated differentiation of preadipocytes from the cells-precursors (fibroblasts and undifferentiated cells of the vascular wall), hypertrophy of preadipocytes (their size and number of nuclei increase) and their proliferation. The process of malignant transformation in a destructive lipoma may be so much pronounced that DNA synthesis may be observed in the mature lipocyte (this has not been described so far).