[New cancers after squamous cell skin cancer].

The subsequent cancer experience in 5,100 patients with squamous cell skin cancer (SCC) was compared with the cancer incidence in the Danish population. Ratios of observed to expected cancers served as the measure of the relative cancer risk (RR). Overall, SCC patients were at significantly increased cancer risk due to cancers of the respiratory organs (RR = 1.7); cancers of the lip, buccal cavity and pharynx (RR = 3.1); non-Hodgkin's lymphoma (RR = 2.3); leukaemia (RR = 2.5); malignant melanoma (RR = 2.6); and small intestine cancers in men (RR = 4.1). The risk of new cancers was higher in patients diagnosed with SCC before the age of 60 years than in those diagnosed with SCC after that age. A previously undocumented, significant excess of smoking-related cancers was observed after a diagnosis of SCC. Since a variety of other squamous cell cancers have been linked to smoking, the authors hypothesize that some general effect of smoking might act on all human squamous epithelia.