Background Oral premalignant lesions (OPML) are frequently extensive and multifocal leading high morbidity for patients. Although oral squamous carcinoma (OSCC) in non‐smoker patients is increasing, little is known about OPML and the carcinogenesis process in these patients. The aims of the study were to insight and compare the clinicopathological and molecular characteristics of OPML of non‐smoker and smoker patients from which one or multiple OSCC have developed. Methods Eighty‐one patients showing extensive and/or multifocal OPML were included in the survey. HPV and EBV were investigated by PCR and in situ hybridization respectively. Cytogenetic studies were performed by microarray in sequential progressive 30 lesions; p53 expression was investigated by immunohistochemistry. Results The patients were 41 males and 40 females, ages ranging from 32 to 93 years (median 64); 43 (53%) were smokers. Non‐smokers were more frequently female with a median age of 68, whereas smokers were men with a median age of 60 (P = 0.005). HPV and EBV were negative in all cases. The most consistent and earliest cytogenetic alterations in both non‐smokers and smokers were loss of heterozygosity (LOH) and losses of locus harboring tumor suppressor genes. Progression to high‐grade dysplasia and OSCC showed progressive addition of LOH, tumor suppressor losses, and oncogenic gains. Conclusion Non‐smoker patients are mostly elderly female and show oral carcinogenic pathways and outcomes similar to smoker patients.

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