Actinic Keratosis

What could be responsible for this pigmented lesion?

David L. Kaplan, MD—Series Editor
University of Missouri Kansas City, University of Kansas

This 57-year-old female presented for routine skin examination and was noted to have an erythematous pigmented lesion on her neck.


What could be responsible?

A. Lentigo maligna. 

B. Pigmented basal cell carcinoma.

C. Pigmented actinic keratosis.

D. Lentigo simplex.

E. Bowen’s disease.

Answer on next page

Answer—Pigmented actinic keratoses

All of the choices were reasonable diagnoses. Therefore, the next step is to do a skin biopsy before proceeding with treatment. Note: Lentigo maligna is usually more variegated in color and pigmented basal cell carcinoma usually has textural changes. 

In the majority of the cases, a collision between a nonpigmented solar keratosis and a separate coexistent pigmented lesion, primarily a solar lentigo, accounts for the pigmentation in pigmented actinic keratoses rather than from any fundamental changes in the quantity or quality of the melanocytes. ■


1.Chung HG, McGuigan KL, Osley KL, et al. Pigmented solar (actinic) keratosis: an underrecognized collision lesion. J Am Acad Dermatol. 2013 Apr;68(4):647-653.