Preservation of cluster 1 small cell lung cancer antigen in zinc-formalin fixative and its application to immunohistological diagnosis.

Monoclonal antibodies reactive with cluster 1 small cell lung cancer antigen have been shown to be useful for the distinction of small cell from non-small cell tumours. In previous studies the antibodies have been applied to frozen sections and cold acetone-fixed tissues. However, one of three monoclonal antibodies that we produced, NCC-LU-243, reacted with some small cell lung carcinomas fixed in formalin solution and embedded in paraffin. The addition of zinc sulphate to the formalin solution at a concentration of 2% (v/w) greatly improved antigen immunoreactivity, and reactivity was retained even after prolonged fixation. Occasionally, immunoreactivity was present in a poorly differentiated adenocarcinoma with rosette-like structures. The monoclonal antibody NCC-LU-243 is thus of considerable potential value in the immunohistochemical diagnosis of small cell lung cancers.