to the editor:The article about actinic keratoses is somewhat misleading. It leaves one with the impression that actinic keratoses most commonly evolves into squamous cell carcinoma. Actually, based on my personal experience during 45 years of practice, basal cell carcinoma is at least 10 times more likely to result from actinic keratoses of the face or ears (squamous cell carcinoma of the lower lip is almost always found in cigarette smokers).

in reply:Basal cell carcinomas, squamous cell carcinomas, and actinic keratoses share common risk factors, such as age, sex, location of residency, occupation (indoor versus outdoor), and propensity to sunburn.¹ Dr. Pentecost makes an excellent clinical point that an actinic keratosis lesion often overlies a basal carcinoma lesion.^2,3

In addition, basal cell carcinomas are a far more common form of nonmelanoma skin cancer than squamous cell carcinomas (80 versus 19 percent, respectively). However, actinic keratosis lesions do not appear to be a precursor to basal cell carcinomas. In a study of 6,000 Australians, a preexisting actinic ker-atosis was a predictive factor for squamous cell carcinomas and basal cell carcinomas. Coexisting actinic keratosis lesions were found in all but one of the 38 patients with squamous cell carcinomas; however, coexisting actinic keratoses were found in 76 of the 124 persons with basal cell carcinomas. This demonstrates that basal cell carcinomas do not require a co-existing actinic keratosis lesion to develop.