Development of carcinoma of the lung as reflected in exfoliated cells

Cytologic examinations of sputum collected periodically since 1957 on a group of uranium miners have been studied and related to the development of bronchogenic carcinoma. Many individuals developed abnormal squamous cell metaplasia that gradually progressed, in several, to develop invasive carcinoma. This progression has been classified into mild, moderate, and marked atypical, squamous cell metaplasias and carcinoma in situ. Cigarette smoking and uranium mining were both associated with the prevalence of these atypias, and with carcinoma in situ and invasive cancer. Neither of these agents, however, appeared to be strongly associated with the duration of the stages of atypia. Age at start of uranium mining was more strongly associated with age at development of carcinoma in situ than other factors tested. There appears to be an average period of 4 or 5 years during which individuals exfoliate cells that are markedly atypical or represent carcinoma in situ in their sputum before developing invasive carcinoma of epidermoid or small cell, undifferentiated varieties. Periodic sputum surveillance of groups at elevated risk of bronchogenic cancer can utilize this period for early detection and treatment.