Thomas L. Petty, MD, Melvyn S. Tockman, PhD, MD, and Branko Palcic, PhD

Cytologic detection of lung cancer in sputum can be traced to the 1930s, 1940s, and 1950s. Dr. Papanicolaou, famed for his development of the pelvic Pap test, also described sputum cytology in the mid-1940s. Other great leaders, such as the late Drs. Liebow, Farber, Bickerman, Barach, and Frost, described various clinical techniques for the detection of lung cancer.

One of the authors (TLP) was a first-year resident at the University of Michigan in 1959 when pathologist Walter Umiker announced at chest conferences that "two sputum cytologies were equal to one biopsy." Later, the authors met Geno Saccomanno of Grand Junction, Colorado, the person who popularized, standardized, and studied sputum cytology more than any other person in the world. The late Saccomanno's atlas of Diagnostic Pulmonary Cytology is a collector's item. In visionary articles introduced to the literature 2 decades ago, Saccomanno's late colleagues, Don Greenberg and John Frost, also prophesied that sputum cytologic diagnosis one day would yield to automated methodology.

Papanicolaou and Saccomanno described the morphologic progression of cytologic atypia through progressive stages of dysplasia to squamous cancer. This epidermoid progression has characterized roentgenographically occult central lesions, most of which are squamous cell carcinomas. Now, using molecular markers of neoplasia, all major lung cancer cell types have been detected by cells exfoliated into the sputum. A well studied cohort of patients in Grand Junction has revealed that roentgenographically occult lung cancer identifies patients with a high percentage (more than 80%) of stage 0 or stage 1 cancer, whereas the actual 5-year cure by surgery in 27 cases was excellent. Subsequent cancers also were identified by sputum cytology or advanced im- aging techniques in a follow-up of this cohort.

Today, there is a growing interest in the early identification of asymptomatic lung cancer by CT scan imaging techniques. This interest is, in large part, the influence of the initial report of the Early Lung Cancer Action Project (ELCAP), which showed that smokers older than the age of 60 years had a prevalence of lung cancer of 2.7%, most of which were early stage lesions. ELCAP has led to a rethinking of the likelihood of cost-effective identification of lung cancer at an early stage (stage shifting) through screening. Early reports of helical CT scan screening, however, detected primarily (peripheral) adenocarcinomas and not the expected numbers of (central) squamous

From the University of Colorado Health Sciences Center, Denver, Colorado; Rush-Presbyterian-St. Luke's Medical Center, Chicago, Illinois; and the National Lung Health Education Program, Denver, Colorado (TLP); Center for Molecular Screening Programs, H. Lee Moffitt Cancer Center and Research Institute, Tampa, Florida (MST); and the University of British Columbia, Vancouver, British Columbia, Canada (BP)