Lipid fixation for fat staining in paraffin sections applied to lesions of atherosclerosis

A new method to fix lipids for staining in paraffin sections was applied here to early lesions of atherosclerosis to test comparability with similar results using frozen-section fat stains. Small blocks of formalin-fixed human coronary artery were exposed to an emulsion of linoleic acid and lecithin in 70% ethylene glycol at 56°C for 3 days. The unsaturated fatty acids partitioned into the tissue lipids for later fixation by chromic acid and could then be processed through paraffin-section for fat staining. Blocks of tissue from the same specimens were also processed for standard frozen-section fat staining. The types of early atherosclerotic lesions described by the American Heart Association Lesions Committee—types I, II, III, and IV—were demonstrated equally well using the two methods. Additional newly described patterns of lipid deposits were also revealed by both methods. The paraffin method showed no indication of omitting or adding anything compared with frozen sections. The surprising finding of unexpected patterns of lipid distribution in human coronary artery suggests that the method may prove to be useful. Those novel patterns were first observed with the more flexible paraffin method and later confirmed by the more tedious and demanding frozen-section method.