Selected Non-neoplastic and Benign Diseases of the Endometrium and Myometrium

Metaplasia of the endometrium represents a change from one epithelial type to another, the latter typically being of a cell type seen elsewhere in the mullerian tract. The aforementioned “change” may be conceptualized as a reactive alteration in the cellular cytoplasm and nuclei, although the precise causative factors are not always clear in each individual case. Table 2.1 summarizes the distribution and frequencies of endometrial metaplasias. In 58–82% of cases, a metaplasia of one type is admixed with a metaplasia of another type. Metaplasias may be associated with a variety of neoplastic and non-neoplastic diseases, with benign or malignant neoplasms, with patients of all ages, and with the use of exogenous hormones.