To examine whether a monoclonal antibody, TFS-4, can distinguish small-cell lung cancer from non-small-cell lung cancers, an extensive survey of fresh lung tumors, cancers from other organs, and normal tissue specimens has been carried out. The antibody has been shown to react specifically with small-cell lung cancer (15 of 15) but not with squamous cell carcinoma (0 of 20), adenocarcinoma (0 of 20) of the lung, or large-cell lung cancer (0 of 2). It reacted neither with other malignancies,

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... uding colorectal cancer, gastric cancer, and malignant lymphoma, nor with such normal tissues as trachea, lung, liver, pancreas, colon, kidney, spleen, skin, striated muscle, bone marrow, or peripheral blood cells. Interestingly, the antibody cross-reacted with central nervous tissues. The antigenic determinant on small-cell lung cancer and that on human brain were both heat labile and trypsin sensitive, but resisted treatment with neuraminidase, suggesting that they represent similar peptides. TFS-4 may be of clinical use in the diagnosis of small-cell lung cancer, while the antigen may help investigate the nature and origin of small-cell lung cancer.