Squamous Cell Carinoma in situ a.k.a. Bowen's disease is the early stage of skin cancer occurring most often in the sun-exposed areas of the skin in older white males. It's a tumor that develops from the squamous cells which are flat, scalelike cells in the outer layer of the skin (the epithelium). The term "in situ" (borrowed from the Romans) means "in the natural or normal place" and in the case of cancer it means that the tumor cells are still confined to the site where they originated and they have neither invaded neighboring tissues nor metastasized afar. It's persistent, progressive, slightly raised, red, scaly or crusted plaque that can occur anywhere on the skin surface (or on the mucosal surfaces such as the mouth). Treatment options include freezing with liquid nitrogen, cauterization (burning), surgical removal, and chemosurgery.