Abstract
Esterase activity in the human kidney is not visualized in paraffin sections of acetone fixed tissues with Gomori''s technic and only very irregularly with the azo dye method of Nachlas and Seligman. It can be regularly demonstrated with both methods in fresh frozen sections. In 5 of 7 renal carcinomas esterase was found in the cytoplasm of tumor cells if fresh frozen sections were used but not in paraffin-fixed material.