Squamous cell carcinoma in situ (Bowen's disease) is an early form of squamous cell skin cancer. In situ means that the cancer involves only the top layer of skin.

Bowen's disease may involve any area of the body but most frequently occurs on sun-exposed areas of the face, neck, arms, and legs. Bowen's disease occurs in sharply defined, round to irregular scaly patches. On lighter skin, the patch may look red. On darker skin, the colour of the patch may be darker or the same colour as the nearby skin.

People with Bowen's disease may be more likely to develop other skin cancers.