Basal cell carcinoma. Close-up of a brown, raised ulcer-like growth on the ear. This is a basal cell carcinoma, also known as a rodent ulcer. It is one of the 3 main types of skin cancer (the others are squamous cell carcinoma & malignant melanoma). This type of cancer is caused by overexposure to sunlight. Fair-skinned people over 50 are the most at risk. Most basal skin cancers occur on the face. The cancer starts as a small flat nodule and grows slowly eventually breaking down at centre to form a shallow ulcer. Basal cell carcinomas very rarely spread to other parts of the body. Treatment involves the surgical removal of the tumour or radiotherapy.