It begins in the squamous cells found in the outer layer of the skin (epidermis) and in our mucous membranes. The information in this section is only about SCC of the skin. SCC occurs when these normal body cells get out of control, multiply and spread. The cells clump together to form a cancerous (malignant) tumour which can then grow and damage healthy parts of the body. This is primary cancer.

At the earliest stage, it is sometimes called carcinoma in situ. Intraepidermal carcinoma, also known as Bowen’s disease, is a particular type of in situ cancer that can occasionally form an SCC. ‘In situ’ means that the cancer has not spread beyond the top layer of the skin (the epidermis). SCC can also begin from a site affected by actinic keratosis.

Over 90% of people with squamous cell carcinoma can be cured.