This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
[{'content': 'Skin biopsy of a patient shows evidence of malignant melanoma. Which is the common type of malignant melanoma? \nSelect and explain. \nA. Superficial spreading, B. Lentigo maligna melanoma, C. Nodular, D. Acral lentiginous', 'role': 'user'}, {'content': "Answer: A \nExplanation: Superficial spreading melanoma comprises approximately 60% to 70% of melanomas and represents the most common melanoma subtype. They often arise in a preexisting nevus and typically develop as a spreading pigmented plaque with irregular borders and variation in color and surface contour. They often exhibit the classic clinical features of melanoma. Areas of regression may result in pink to white areas within the black or brown tumor. They may progress to a veical growth phase faster than lentigo maligna. Ref: Ludgate M.W., Wang T.S. (2009). Chapter 100. Skin Cancer. In J.B. Halter, J.G. Ouslander, M.E. Tinetti, S. Studenski, K.P. High, S. Asthana (Eds), Hazzard's Geriatric Medicine and Gerontology, 6e.", 'role': 'assistant'}]