Revision of light-microscopic kidney biopsy diagnosis in glomerular disease.

Paraffin-embedded kidney biopsies sent to our laboratory in 1967 were re-embedded in Epon and studied with electron and light microscopy (1-micrometer thick sections). Of 28 biopsies with enough material 18 were cases with clinical suspicion and symptoms of glomerular disease. In electron microscopy all of these were shown to be of glomerular origin by demonstrating either dark deposits in or at the basement membrane, or amyloid fibrils, or areas with retraction of the foot processes of the epithelial cells. Original light microscopy in 1967 had given proof of glomerular origin in 9 of these 18 cases. Light microscopy of plastic sections of these originally paraffin-embedded biopsies was also helpful in diagnosis and showed deposits in 9 out of 14 cases with ultrastructural deposits. The study shows that considerable benefits can be gained through re-embedding biopsies in plastic, especially in cases with minor alterations.