Immunohistochemistry of pigmented actinic keratoses, actinic keratoses, melanomas in situ and solar lentigines with Melan‐A

Distinguishing lentigo maligna from solar lentigo, and pigmented actinic keratosis can sometimes be problematic. Melan‐A is an immunohistochemical marker which that can be helpful in decorating the melanocytes of pigmented lesions. A recent report has suggested that Melan‐A may spuriously label nests of junctional keratinocytes, potentially leading to the misdiagnosis of melanoma in situ . We compared Melan‐A immunohistochemical staining in pigmented actinic keratosis , non‐pigmented actinic keratoses , melanoma in situ of lentigo maligna type and solar lentigines. We found a statistically significant increase of Melan‐A staining in melanoma in situ , but no statistical difference in the number of junctional Melan‐A positively staining cells, in solar lentigines, pigmented actinic keratoses, and non‐pigmented actinic keratoses, respectively. In the non non‐melanoma samples, the Melan‐A A‐positive cells located at the dermal‐epidermal junction were interspersed and not observed in clusters. Increased staining with Melan‐A, in an actinic keratosis, or solar lentigo should raise the possibility of a contiguous melanoma in situ .