Premalignant changes in normal appearing epithelium in patients with squamous cell carcinoma of the upper aerodigestive tract.

Biopsy specimens of "normal" mucous membrane of patients susceptible to the effects of the carcinogens of tobacco revealed morphologic abnormalities on electron microscopic examination that were consistent with the concept that carcinogenesis is a multistep process of sequential neoplastic development extending over a long period of time. Such changes in the upper aerodigestive tract are probably tobacco induced and may be reversible if tobacco exposure is eliminated. Use of the electron microscope can provide the clinician with an accurate assay of the severity of mucosal alterations induced by tobacco. The ability to detect such morphologic abnormalities should provide another deterrant to smoking and a useful tool in the further study of these phenomena.