<prompt> Cocks peculiar tumour is: September 2007Infected sebaceous cystOsteomyelitis of skullCyst in the skullTumour of the skull  <response>: Ans. A: Infected sebaceous cyst Cocks 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 Cocks peculiar tumour. 