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: Skin
[{'content': 'Poor prognostic factor for melanoma is: March 2013 \nSelect and explain. \nA. Size of tumour, B. Spread to lymphatics, C. Shape, D. Colour of tumour', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. B i.e. Spread to lymphatics', 'role': 'assistant'}]