Carcinoembryonic antigen in sputum cytology.

Carcinoembryonic antigen (CEA) activity was studied in exfoliated cells in sputum from patients with carcinoma of the lung and its precursor lesions. For this purpose, immunohistochemical techniques were applied on paraffin-embedded cell blocks of sputum. In the cancer patients, not only the morphologically malignant cells were CEA positive, but squamous cells that lacked the cytologic features of malignancy also were CEA positive. Some of these CEA-positive cells originated in morphologically benign squamous epithelium. In high-risk patients without clinical evidence of neoplasm, some benign squamous cells were CEA positive, possibly indicating the presence of an undetected or developing cancer.