Sputum cells from lung tumor patients carry a cell surface marker not found in normal sputum

Cells were collected from sites of known lung tumours and corresponding control areas of these lungs. Fluorescent staining demonstrated that the tumour cells and epithelial cells (cytologically these cells appeared normal) both possessed a receptor for these fluorescent probes. Fluorescent labelling of sputum cells from these tumour patients also resulted in fluorescent labelling of these "cyto logically normal" epithelial cells. No such fluorescent epithelial cells were observed in sputum samples collected from control subjects or in cells collected from the control areas of the tumour patients' lungs. We conclude that a cell surface protein receptor is expressed in lung tumour-associated epithelial cells but is absent from control sputum epithelial cells.