squamous cell carcinoma in situ (SKWAY-mus sel KAR-sih-NOH-muh in SY-too)
A condition in which abnormal cells are found in the tissues that form the surface of the skin, the lining of the hollow organs of the body (such as the bladder and uterus), and the lining of the respiratory and digestive tracts. These abnormal cells may become cancer and spread into nearby normal tissue. Squamous cell carcinoma in situ occurs in the skin, anus, bladder, uterus, cervix, head and neck, lung, and vagina, and in other parts of the body. Also called stage 0 squamous cell carcinoma.