Skin cancer. Squamous cell carcinoma (SCC) on a patient's lip. An SCC arises from the uncontrolled proliferation of squamous cells, flattened cells in the skin and mucous membranes. It causes the formation of a large, ulcer-like area that, in its later stages, can spread to other parts of the body. This form of cancer is most commonly caused by sunlight. Treatment is by surgical excision. Chemotherapy and radiotherapy may also be needed.