Comparison of formalin- and acetone-fixation for immunohistochemical detection of carcinoembryonic antigen (CEA) and keratin

The purpose of the present study was to compare the relative merits of cold acetone and buffered formalin as fixatives for the detection of carcinoembryonic antigen and keratin in permanently embedded tissues using a peroxidase-antiperoxidase (PAP) immunohistochemical procedure. The effect of treatment with the proteolytic enzyme pronase also was examined in the formalin-fixed tissues. Cold acetone was found to be superior to formalin for the preservation of CEA and keratin antigenic activities in a variety of benign and malignant tissues. Pronase treatment markedly increased the staining intensities of both antigens in formalin-fixed tissues. For many tissues, however, superior results were obtained using the cold acetone method, and this technic is recommended for the optimum retention of antigenic activity in permanently embedded tissues.