Sputum cytology for the diagnosis of carcinoma of the lung.

Of 400 consecutive patients with histologically proven carcinoma of the lung, one to six sputum samples (mean, 2.8) were examined cytologically; 60% also had histologic examination of paraffin-embedded material. The overall sensitivity of sputum cytology was 0.58. The sensitivity increased from 0.37 to 0.57 when three samples rather than one were examined; it increased by only another 0.01 when four to six samples were studied. The examination of paraffin-embedded material yielded another 0.075 increase in sensitivity. A multiparametric study, including diameter, cavitation, site and histologic type of the pulmonary tumors, showed that sputum cytology was particularly significant for neoplasms of the left upper lobe and that the sensitivity related to the histologic type was not independent of the site, diameter and cavitation. The overall cytologic typing accuracy was 0.77, with a range from 0.20 to 0.96. The majority of the diagnoses at variance with histology and the unclassified malignant epithelial tumor cells were found to be associated predominantly with carcinoma of the large-cell type and with poorly differentiated adenocarcinomas.