Phototherapy has played a major role in the treatment of various skin diseases, including psoriasis, atopic dermatitis, and vitiligo.^1,2 Given the chronic and relapsing nature of such skin diseases, patients often receive multiple courses of phototherapy during their lives. There have been concerns about whether repetitive exposure to UV light during long-term phototherapy would increase the risk of photocarcinogenesis³ because UV is well known to cause nonmelanoma skin cancers (NMSCs) and melanoma.^3,4 Among the various types of phototherapy, psoralen plus UV-A (PUVA) phototherapy has been found to be associated with an increased risk of skin cancers,^5-7 but it is not currently widely used. The widespread use of indoor tanning has raised concerns about an increased risk of skin cancer and many dermatologists are strongly opposed to indoor tanning.⁸ However, to our knowledge, the risk of skin cancer after long-term narrowband UV-B (NBUVB) phototherapy, which is now widely used for therapeutic purposes in dermatology, has not been fully investigated.^5,9,10

This descriptive study was aimed to examine trends in the incidence of melanoma and nonmelanoma in South Korea. The nationwide incidence data for melanoma and non-melanoma skin cancer was obtained from the Korea Central Cancer Registry. Age-standardized rates were calculated and analyzed, using a Joinpoint regression model. The incidence of basal cell carcinoma has increased dramatically both in men (average annual percentage change [AAPC], 8.0 [95% confidence interval (CI), 6.0 to 10.1]) and women (AAPC, 9.0 [95% CI, 7.5 to 10.4]). Squamous cell carcinoma has also steadily increased both in men (AAPC, 3.3 [95% CI, 2.6 to 4.0]) and women (AAPC, 6.8 [95% CI, 5.3 to 8.4]). Cutaneous melanoma increased continuously from 1999 to 2014 inwomen (AAPC, 3.5 [95% CI, 2.4 to 4.6]), whilst rapidly increasing in men until 2005 (APC, 7.9 [95% CI, 2.4 to 13.7]) after which no increase has been observed (APC, ‒0.2 [95% CI, ‒2.3 to 2.0]). The incidence rates of melanoma and non-melanoma skin cancer have increased over the past years, with the exception of melanoma in men. Further studies are required to investigate the reasons for the increased incidence of these skin cancers in South Korea.

High-intensity focused ultrasound (HIFU) and radiofrequency (RF) are used for non-invasive skin tightening. Neocollagenesis and neoelastogenesis have been reported to have a mechanism of controlled thermal injury. To compare neocollagenesis and neoelastogenesis in each layer of the dermis after each session of HIFU and monopolar RF. We analyzed the area fraction of collagen and elastic fibers using the Masson's Trichrome and Victoria blue special stains, respectively, before and after 2 months of treatments. Histometric analyses were performed in each layer of the dermis, including the papillary dermis, and upper, mid, and deep reticular dermis. Monopolar RF led to neocollagenesis in the papillary dermis, and upper, mid, and deep reticular dermis, and neoelastogenesis in the papillary dermis, and upper and mid reticular dermis. HIFU led to neocollagenesis in the mid and deep reticular dermis and neoelastogenesis in the deep reticular dermis. Among these treatment methods, HIFU showed the highest level of neocollagenesis and neoelastogenesis in the deep reticular dermis. HIFU affects deep tissues and impacts focal regions. Monopolar RF also affects deep tissues, but impacts diffuse regions. We believe these data provide further insight into effective skin tightening.