Dermatoscopy of pigmented actinic keratosis--a striking similarity to lentigo maligna.

BACKGROUND: Pigmented actinic keratosis (PAK) resembles lentigo maligna (LM) clinically and histopathologically in some cases.

OBJECTIVES: To describe the dermatoscopical characteristics of this uncommon variant of actinic keratosis and evaluate whether these characteristics show common features with LM.

OBSERVATIONS: We had the opportunity to examine a 78-year-old woman who presented with a PAK lesion on her face dermatoscopically and histopathologically. The pigmented pseudo-network had black and gray dust in some areas, which were the main dermatoscopical features. The pigmented pseudo-network was formed by an unhomogenous brown background interrupted by regularly distributed hair follicules. The hyperpigmentation was based not only on an increased presence of melanin within the keratinocytes in the basal and spinous layers of epidermis, but also an intensive apoptosis of keratinocytes connected to numerous melanophages.

CONCLUSIONS: The dermatoscopical picture of PAK in this patient was practically indistinguishable from the early stage of LM. The authors considered that the pigmented atypical melanocytes' role in LM presenting as black dots in the dermatoscopical picture was displayed by the individually pigmented keratinocytes in PAK. The groups of melanophages presenting as gray dust were present in PAK similarly to their presentation in LM. The character of the pigmented pseudo-network is the same in the both afflictions. There is a need to examine other cases of PAK in order to decide whether our case represents a general pattern of the dermatoscopical picture.