Spreading pigmented actinic keratosis.

We present four cases of spreading pigmented actinic keratoses, an only recently described pigmented lesion of sun-exposed areas, in which the histologic appearance is that of actinic keratosis with the additional feature of excessive melanin deposition in the lower epidermis and in the upper dermis. Clinically, it is a brown patch or plaque with a smooth surface, usually larger than 1 cm, that tends to spread centrifugally. Clinical differential diagnoses include seborrheic keratosis, melanocytic nevus, senile lentigo, lentigo maligna, and lentigo maligna melanoma. This pigmented lesion is probably much more common than the existing literature would indicate.