A 79-year-old man presents for a routine skin check, in the context of his 40-year history of nonmelanoma skin cancer. He grew up on a farm and then became a farmer himself, spending almost every day in the sun (usually without a hat). His skin burned easily but would take on a “tan” by the start of summer.
In the succeeding years, he developed so many skin cancers (and had them removed) that he lost count. All were basal cell or squamous cell carcinomas, predominately manifesting on his face, arms, and ears. Several required Mohs surgery for removal.
Abundant evidence of excessive sun exposure is seen on the patient’s skin: actinic keratoses on the forehead, ears, and neck, and multiple solar lentigines on the face, neck, and arms. On his left neck, below the ear, is a large, oddly pigmented, dark macular patch. Dermatoscopic examination reveals focal pigmentary clumping and streaming, which prompts the decision to perform an incisional biopsy. The darkest and most irregular part of the lesion is taken as a sample. The pathology report shows lentigo maligna.
What is lentigo maligna?