Abstract 5161: Development of cutaneous basal cell carcinomas from cutaneous actinic keratoses

Abstract

Abstract Actinic keratoses (AKs) are extremely common proliferations of epidermal keratinocytes which show cytological atypia and impaired ability to mature as the cells that comprise them migrate from the basal layer of the epidermis to higher levels of the epidermis. A small percentage of AKs are well known to progress to cutaneous squamous cell carcinomas (SCCs). However, progression of AKs to cutaneous basal cell carcinomas (BCCs) has not been convincingly documented despite several attempts, even though BCCs are significantly more common than SCCs in the general US and European populations. Documented cases have been dismissed as actinic keratoses that have simply occurred superimposed upon basal cell carcinomas due to chance occurrence of two common sun induced skin lesions at the same sites. In a university based referral dermatopathology service, one of us (WCL) observed 21 cases of AKs progressing to BCCs during a 29 year period (January 1, 1985 to December 31, 2013) of continuous observation in which 115,898 cases of AKs, 10,188 cases of BCCs and 4,809 cases of SCCs were diagnosed. Only cases in which a continuous progression of cells from those showing changes typical of AKs to those showing changes typical of BCCs was observed were included. During the same interval 308 cases of AKs progressing to SCCs were diagnosed. To further test the hypothesis that AKs can progress to BCCs, cases of AKs that progressed to BCCs were further examined to determine those in which neither the AK nor the BCC occupied the entire skin surface (i.e., length of the epidermal basement membrane) present in the specimen. Of the 21 cases, 13 met this criterion. All were shave biopsies of sun damaged skin. For each biopsy, the proportion of the surface covered by the AK, the proportion occupied by the BCC, and the proportion of the surface overlapped by both lesions were measured and the proportion of overlap was compared to the proportion of overlap expected due to chance. Statistical analysis showed that the observed overlap exceeded the expected overlap by 32 per cent with p < 0.05. We conclude that progression of AKs to BCCs, while not as common as progression of AKs to SCCs, does occur in a small proportion of cases. Citation Format: W Clark Lambert, Claude E. Gagna, Muriel W. Lambert. Development of cutaneous basal cell carcinomas from cutaneous actinic keratoses. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 5161.