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': "Cock's peculiar tumour is: September 2007 \nSelect and explain. \nA. Infected sebaceous cyst, B. Osteomyelitis of skull, C. Cyst in the skull, D. Tumour of the skull", 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. A: Infected sebaceous cyst Cock's peculiar tumour is a sebaceous cyst linked growth. One form of sebaceous cyst is the trichilemmal cyst; these are thought to arise from the hair follicle epithelium and are most commonly found on the scalp. Usually they are multiple but occasionally there can be a proliferating trichilemmal cyst which grows to a large size and ulcerates. These can resemble a squamous cell carcinoma (both clinically and histologically) and these ulcerating solitary cysts are called Cock's peculiar tumour.", 'role': 'assistant'}]