It seems I have something called Bowen's disease on my back in 3 places. It is apparently a blemish that if not treated may turn into cancerous tissue.

The NHS definition of it.

Bowen's disease

Bowen's disease is a very early form of skin cancer that's easily treatable. The main sign is a red, scaly patch on the skin.

It affects the squamous cells, which are in the outermost layer of skin, and is sometimes referred to as squamous cell carcinoma in situ.

The patch is usually very slow growing, but there's a small chance it could turn into a more serious type of skin cancer if left untreated.

The most effective method of reducing your risk of Bowen's disease, as well as other more serious types of skin cancer, is to limit your exposure to the sun.