Diffuse macular melanosis of the buccal mucosa, lateral tongue, palate, and floor of the mouth is occasionally seen among cigarette smokers(Figure 6-8). Although no cause-and-effect relationship has been proven and although most smokers (even heavy smokers) usually fail to show such changes,
those who do are said to exhibit smoker’s melanosis. Thus, it is probable that in certain individuals, melanogenesis is stimulated by tobacco smoke products. Indeed, among dark-skinned individuals who normally exhibit physiologic
pigmentation, studies have disclosed that tobacco use stimulates an increase in oral pigmentation. The lesions are brown, flat, and irregular; some are even geographic or maplike in configuration. Histologically, basilar melanosis with melanin incontinence is observed, and the lesions have no premalignant potential.