A novel monoclonal antibody, SCCL 175, with specificity for small cell neuroendocrine carcinoma of the lung.

The murine monoclonal antibody SCCL 175, which is one of several monoclonal antibodies directed against small cell neuroendocrine carcinoma developed by one of us (E.D.B.), was studied for its immunohistochemical reactivity against normal human tissues and a spectrum of bronchopulmonary and metastatic carcinomas using the avidin-biotin complex technique. SCCL 175 reacted with 40 of 44 small cell carcinomas including both primary and metastatic sites and was distributed both on the cell surface and intracytoplasmically. Staining was seen in fresh frozen tissues, cytology preparations, and in a limited number of paraffin-embedded tissue sections after trypsin pretreatment. It was nonreactive with all non-small cell lung carcinomas, neuroendocrine carcinomas from other primary sites, and nonpulmonary carcinomata studied to date. Its distribution in normal adult human tissues was limited to some hypothalamic neurons and the apical membranes of renal proximal tubular epithelium. Cytotrophoblastic and syncytotrophoblastic cells from placental tissue demonstrated variable SCCL 175 immunoreactivity. Of choriocarcinomas studied, one of three demonstrated focal staining. These findings demonstrate the diagnostic utility of SCCL 175 in phenotyping small cell carcinoma of lung, and its specificity suggests a potential role in the therapy of this disease.