Pigmented Actinic Keratosis: Case Report and Review of an Uncommon Actinic Keratosis Variant that can Mimic Melanoma

Pigmented actinic keratosis is an uncommon variant of actinic keratosis that can mimic melanocytic lesions. A 54-year-old man who presented with a dark lesion on his nasal tip is described; biopsy of the lesion revealed a pigmented actinic keratosis that was treated with cryotherapy using liquid nitrogen. Pigmented actinic keratoses typically appear on sun-exposed areas of the skin as flat hyperpigmented lesions that grow in a centrifugal pattern. Dermoscopy reveals one or more pseudonetworks with hyperpigmented dots or globules. Histopathology shows atypical keratinocytes in the epidermal basal layer and increased melanin content in the epidermis and dermis. Treatment options include liquid nitrogen cryotherapy for solitary lesions and curettage, 5-fluorouracil, imiquimod, ingenol mebutate, photodynamic therapy, or superficial peels for extensive lesions.