a lesion characterized by cytologic changes of the type associated with invasive carcinoma, but with the pathologic process limited to the lining epithelium and without histologic evidence of extension to adjacent structures; the distinctive changes are usually more apparent in the nucleus, i.e., variation in size and shape, increase in chromatin, and numerous mitoses (including some that are atypical) in all layers of the epithelium, with loss of orderly maturation. The lesion is presumed to be the histologically recognizable precursor of invasive carcinoma, i.e., a localized and curable phase of carcinoma. SYN: intraepithelial carcinoma.