Harvind S. Chahal, BA, Kerri E. Rieger, MD, PhD, and Kavita Y. Sarin, MD, PhD Department of Dermatology, Stanford University School of Medicine, California Funding sources: Dermatology Foundation (Dr Sarin) and Stanford Medical Scholars Research Program (Mr Chahal). Conflicts of interest: None declared. Correspondence to: Kavita Y. Sarin, MD, PhD, Department of Dermatology, Stanford University Medical Center, 450 Broadway St, Pavilion C, 2nd Floor, Redwood City, CA 94063 E-mail: ksarin@stanford.edu REFERENCES 1. Lever WF, Elder DE, eds. Lever’s histopathology of the skin. 10th ed. Philadelphia (PA): Wolters Kluwer, Lippincott Williams and Wilkins; 2009. 2. Miller DL, Weinstock MA. Nonmelanoma skin cancer in the United States: incidence. J Am Acad Dermatol. 1994;30(5 Pt 1): 774-778. 3. Yiannias JA, Goldberg LH, Carter-Campbell S, Reddick M, Chamberlain RM. The ratio of basal cell carcinoma to squamous cell carcinoma in Houston, Texas. J Dermatol Surg Oncol. 1988;14(8):886-889. 4. Rogers HW, Weinstock MA, Feldman SR, Coldiron BM. Inci- dence estimate of nonmelanoma skin cancer (keratinocyte carcinomas) in the US population, 2012. JAMA Dermatol. 2015; 151:1081-1086. 5. Chahal HS, Lin Y, Ransohoff KJ, et al. Genome-wide association study identifies novel susceptibility loci for cutaneous squa- mous cell carcinoma. Nat Commun. 2016;7:12048. 6. Stern RS. Prevalence of a history of skin cancer in 2007: results of an incidence-based model. Arch Dermatol. 2010;146(3):279-282. http://dx.doi.org/10.1016/j.jaad.2016.08.019 The detection of human papillomaviruse16 in squamous cell carcinoma of the nail unit: A case series To the Editor: The correlation between human papillomavirus (HPV) and squamous cell carcinoma (SCC) of the skin and adnexa is still controversial. 1 The detection of the virus has been described in several case series of nail unit SCC. 2,3 This study aimed to evaluate the presence of HPV in a series of 41 cases of nail unit SCC referred to our dermatology skin cancer unit between January 2006 and December 2014. The study was carried out on residual biopsy sections after diagnostic analysis in the course of institutional diagnostic services and was exempted from institutional review board review. The INNO-LiPA HPV Genotyping Extra assay (Fujirebio, Pomezia, Italia Srl) was used to detect 28 mucosal HPV, including 18 high-risk and prob- able high-risk HPV (16, 18, 26, 31, 33, 35, 39, 45, 51, 52, 53, 56, 58, 59, 66, 68, 73, 82), 7 low-risk HPV (6, 11, 40, 43, 44, 54, 70), and 3 undetermined-risk HPV (69, 71, 74). All samples were amplified in real-time polymerase chain reaction (PCR) with a primer pair specific for the E6 region of HPV-16 to avoid false negatives because of the loss of the L1 region, resulting from viral integration in cancer cells. Finally, a nested PCR (FAP nested PCR) was used for the detection of a broad spectrum of cutaneous -HPV; a consensus outer primer pair FAP 59/6415 and a consensus inner primer pair FAP 6085/6319 were used for end point PCR amplification. Table I shows patients’ demographic data, and clinical and histopathologic characteristics of the Table II. Lifetime prevalence of basal cell carcinoma and squamous cell carcinoma in Caucasians, stratified by age group Age, y #30 31-45 46-60 [60 Combined BCC 0.1% (42) 0.8% (650) 4.1% (3194) 10.6% (9059) 4.5% (12,945) SCC 0.0% (12) 0.2% (199) 1.6% (1263) 6.0% (5105) 2.3% (6579) BCC:SCC 3.5:1 3.3:1 2.5:1 1.8:1 2.0:1 Lifetime prevalence values are reported as percentages, with number of self-reported cases in parentheses. To calculate each percentage, the number of cases in an age group was divided by the total number of subjects (cases plus controls) within that age group. Data source: 23andMe (Mountain View, CA) research participants with at least 97% European ancestry. BCC cases, SCC cases, and both sets of controls had 52%, 53%, and 54% males, respectively. Participants provided informed consent to take part in this research, in accord with 23andMe human subjects protocol (reviewed and approved by Ethical and Independent Review Services, an Association for the Accreditation of Human Research Protection Programs, Inceaccredited institutional review board). For more information about this cohort, please contact the corresponding author (ksarin@stanford.edu) or see: a. Pickrell JK, Berisa T, Liu JZ, et al. Detection and interpretation of shared genetic influences on 42 human traits. Nat. Genet. 2016. http://dx. doi.org/10.1038/ng.3570. b. Chahal HS, Lin Y, Ransohoff K, et al. Genome-wide association study identifies novel susceptibility loci for cutaneous squamous cell carcinoma. Nature Commun. 2016;7(12048):1-8. http://dx.doi.org/10.1038/ncomms12048. c. Chahal HS, Wu W, Ransohoff K, et al. Genome-wide association study identifies 14 novel risk alleles associated with basal cell carcinoma. Nature Commun. 2016;7(12510):1-10. http://dx.doi.org/10.1038/ncomms12510. BCC, Basal cell carcinoma; SCC, squamous cell carcinoma. JAM ACAD DERMATOL FEBRUARY 2017 354 Research Letters