Invasive and in situ squamous cell carcinoma of the skin: a nationwide study in Iceland

Background The worldwide incidence of cutaneous squamous cell carcinoma (cSCC) is increasing. Objectives To evaluate the tumour burden of in situ and invasive cSCC in Iceland, where the population is exposed to limited ultraviolet radiation. Methods This whole-population study used the Icelandic Cancer Registry, which contains records of all in situ and invasive cSCC cases from 1981 to 2017. Incidence of cSCC was evaluated according to age, anatomical location, residence and multiplicity, and trends were assessed using joinpoint analysis. Age-standardized rates (WSR) and age-specific incidence rates per 100 000 person-years were calculated, along with cumulative and lifetime risks. Results Between 1981 and 2017, in situ cSCC WSR increased from 1 center dot 2 to 19 center dot 1 for men and from 2 center dot 0 to 22 center dot 3 for women. Invasive cSCC WSR rose from 4 center dot 6 to 14 for men and from 0 center dot 3 to 13 center dot 2 for women. The average number of in situ cSCC lesions was 1 center dot 71 per woman and 1 center dot 39 per man. Women developed more in situ cSCCs than invasive cSCCs in almost all anatomical locations, whereas men developed more invasive cSCCs, mostly on the head and neck. The rates of in situ cSCC were higher in Reykjavik compared with rural areas. Furthermore, women more commonly developed multiple in situ lesions. For lip cSCCs, invasive lesions occurred more frequently than in situ lesions among both sexes. Joinpoint analysis showed that in situ cSCC in women exhibited the most rapid incidence increase. Conclusions cSCC has become an increasingly significant public health problem in Iceland. Tanning bed use and travelling abroad may contribute to skin cancer development. Public health efforts are needed to stem the behaviours leading to this rapid rise in cSCC.