You are answering a USMLE-style medical question. Question: A 67-year-old white man presents to his primary care provider for an annual examination. He notes a pink bump that has rapidly developed on his forehead over the last month. In the past, he has had significant sun exposure including multiple blistering sunburns. The physical examination reveals a 2 cm dome-shaped plaque with a central keratin plug (as shown in the image). Excisional biopsy of the lesion reveals an exophytic nodule with central invagination, full of keratin. Keratinocyte atypia is minimal. Which of the following is the most likely diagnosis? Options: A) Keratoacanthoma B) Basal cell carcinoma C) Seborrheic keratosis D) Kaposi's sarcoma Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.