New dark lesion on nose o...

A 54-year-old man presented a new dark lesion on his nose to the clinic. The asymptomatic lesion had been present for a year and had progressively increased in size. The clinical examination of his face showed a 5 x 5-mm black patch on the nasal tip, as shown in the figure. However, a complete evaluation of his entire body did not show any similar lesions. Therefore, a 2-mm punch biopsy was performed. Microscopic examination of hematoxylin and eosin-stained sections showed a proliferation of atypical keratinocytes in the lower layers of the epidermis with overlying parakeratosis. There was sparing of adnexal epithelium. However, the lesion expanded to the lateral margins of the specimen. Immunohistochemical stains showed that MART-1 and MiTF did not stain the atypical cells. Therefore, an atypical melanocytic proliferation was excluded. Hence, upon the correlation of the history, clinical presentation, and pathologic findings, a pigmented actinic keratosis diagnosis was established