Carcinoma in situ* is cancer of the oral
epithelium which is confined to the epithelial
layer. It presents most commonly as a persistent
red plaque (erythroplakia) or a mixed white and
red plaque. It may also appear as a leukoplakia.
Complete removal is the treatment. When
completely removed, the prognosis is excellent,
although the patient is at increased risk of
developing new lesions at other locations on the
oral mucosa.