Squamous cell carcinoma antigen (SCC)

Squamous cell carcinoma antigen is a protein produced by squamous epithelial cells — the flat, surface-lining cells that cover the skin and line passages such as the cervix, airways, mouth and throat, and oesophagus. When a squamous cell cancer arising in these tissues grows, more of the antigen is released into the blood, so the level tends to reflect the amount of active disease. Its main uses are in monitoring known squamous cell cancers of the cervix, the lung (squamous type), and the head and neck. In someone being treated, a falling SCC level suggests the treatment is working, while a rising trend over repeated tests can be an early clue that the disease is becoming more active, prompting imaging and reassessment. It is not a screening test and cannot make a diagnosis on its own, because it is not specific: it can be mildly raised by common benign skin conditions such as eczema and psoriasis, and by reduced kidney function, and it is often normal in early cancer. The specialist interprets the trend within the full clinical picture, often alongside other markers.

• Squamous cell cancer (cervix, lung, head and neck) — the main use; higher levels reflect more active disease and are followed during treatment.
• A rising trend in known disease — can signal the cancer becoming more active.
• Benign skin conditions — eczema, psoriasis and other skin disease can cause mild, non-cancer rises.
• Reduced kidney function — can raise the level independently.
• A single mildly raised value — often non-specific and needs the trend and clinical context.

• Normal or low — the expected result, and reassuring during monitoring.
• A falling level during treatment — suggests the therapy is working.
• Not a rule-out — a normal SCC antigen does not exclude cancer.