Actinic keratoses

• Most common premalignant skin condition.
• Dysplastic proliferations of keratinocytes with a potential for malignant transformation (1).
• Characterized by multifocal scaly, hyperpigmented or scaly lesions, usually brown with a scaly base.
• Histologically they are characterised by marked thickening of the keratin layer (hyperkeratosis) and the prickle cell layer (acanthosis). There may be a variable degree of dysplastic change and abnormal mitotic activity. However the basal layer remains intact.

Note 1 - there is debate whether actinic keratoses are premalignant conditions or alternatively early-stage squamous cell carcinoma (SCC). In a study of 459 patients with cutaneous SCC, there were associated adjacent actinic keratoses in 97% of the cases of cutaneous SCC (2).

Note 2 - there has been tremendous variation in the reported risk of progression of actinic keratosis to invasive SCC (between 0.025% to 16% per year). There is currently no existing technology to distinguish between actinic keratosis lesions that will clear, remain stable, or progress to invasive disease. (3)

Click here for example images of this condition

Reference:

• (1) Reinehr CPH, Bakos RM. Actinic keratoses: review of clinical, dermoscopic, and therapeutic aspects. An Bras Dermatol. 2019 Nov-Dec;94(6):637-657. doi: 10.1016/j.abd.2019.10.004. Epub 2019 Nov 6. PMID: 31789244; PMCID: PMC6939186.
• (2) Hurwitz RM, Monger LE. Solar keratosis: an evolving squamous cell carcinoma. Benign or malignant? Dermatol Surg. 1995 Feb;21(2):184. doi: 10.1111/j.1524-4725.1995.tb00141.x. PMID: 7894943.
• (3) Glogau RG. The risk of progression to invasive disease. J Am Acad Dermatol. 2000 Jan;42(1 Pt 2):23-4. doi: 10.1067/mjd.2000.103339. PMID: 10607353.