At the insistence of his wife, a 39-year-old man presents to dermatology for evaluation of a lesion on his neck that manifested three years ago. As the lesion has grown, darkened, and become more irregular in outline, she has urged him to have it checked. Her efforts finally succeeded when several of his coworkers also commented on it.
The patient has a history of sun exposure but says he tolerates it well and tans easily. He is otherwise healthy.
EXAMINATION
The irregularly pigmented and bordered dark brown macule, located on the lateral aspect of the left side of his neck, measures about 2 cm in its greatest dimension. The rest of his neck shows definite signs of chronic UV overexposure, in the form of poikilodermatous changes.
Dermatoscopic examination of the lesion shows focal areas of pigment streaming and blue veiling—both indicative of melanoma. In light of these findings and in the context of his heavily sun-damaged skin, the patient is scheduled for excision. This is performed one week later; the lesion is removed with 5-mm margins, producing a curved, elliptiform defect to match local skin lines, with a two-layer closure.
What is the diagnosis?