Discrimination of human small cell and non-small cell lung tumors by a panel of monoclonal antibodies.

The immunohistochemical reactivity of biopsy specimens from different human lung tumor cell types was examined with 4 human small cell lung carcinoma (SCLC)-reactive monoclonal antibodies (MoAbs) (SCLC 1096, SCLC 2051, SCLC 3121, and SCLC 5023) generated in this laboratory, with the use of Formalin-fixed, paraffin-embedded tissue sections. Each MoAb reacted preferentially with SCLC tumors (62-97% of 29 cases tested), with low-to-moderate cross-reactivity with non-SCLC tumors (SCLC 1096, 13.7%; SCLC 2051 and SCLC 3121, 9.8% each; SCLC 5023, 41%, of 51 cases tested). None of the 4 MoAbs reacted with nonmalignant lung biopsy specimens. SCLC tumors were characterized by their collective immunoperoxidase reactivity with the MoAb panel of SCLC 2051, SCLC 3121, and SCLC 5023. Based on unequivocal positive reactions with at least 2 of the 3 MoAbs, this MoAb panel correctly identified 97% (28/29) of SCLC cases of 80 lung tumor cases tested. By contrast, only 4 of 51 (7.8%) non-SCLC cases were positive by the same criterion. These observations suggest that immunohistochemical analysis with these SCLC-reactive MoAbs could help in discriminating small cell from other human lung carcinoma cell types.