Lipid-rich cell thyroid adenoma: histopathology with comparative lipid analysis.

A second case of the unique lipid-rich cell thyroid adenoma is described complemented by detailed lipid analysis. New observations were made. The cytoplasm of the tumour cells contained scattered, aggregated sudanophil crystals; under polarized light the frozen, unstained sections exhibited numerous birefringent lipid crystals; electron microscopy provided further evidence that the clear cell appearance was due to intracellular lipid droplets with scanty glycogen particles. Comparative lipid analysis by thin layer chromatography and high-pressure liquid chromatography (HPLC) revealed quantitative and qualitative differences in lipid composition of tumour cells when compared with goitre cells from normal thyroid gland and subcutane fat. Qualitative differences in triglyceride composition (by HPLC) between tumour cells and subcutaneous fat indicated that the fat accumulation in the follicle cells was not a result of simple storage, but an expression of altered intracellular lipid metabolism.