Precancerous lesions of the endometrium.

The existence of precancerous lesions of the endometrium is well established, but differences in terminology and difficulties in the interpretation of published studies have complicated quantitation of the malignant potential of the descibed subtypes. Clinical investigations, cellular studies, chromosome and DNA analyses, and animal experiments suggest that the malignant potential of cystic hyperplasia is low in contrast to that of the more complex types of hyperplasia. The significance of atypical secretory hyperplasia, squamous metaplasia, and endometrial polyps in the evolution of endometrial cancer has not been investigated adequately. Artifactual crowding of glands due to fragmentation and benign processes such as the epithelial regeneration in late menstrual endometrium and the Arias-Stella reaction should not be confused with precancerous changes. A classification of precancerous lesions is presented and the need for adoption of a uniform terminology for future investigations and communication with gynecologists is emphasized.