The terminology of simple hyperplasia, complex hyperplasia, and atypical hyperplasia has been recommended: Simple hyperplasia includes those with cystic and branching adenomatous patterns. Complex hyperplasia refers to the presence of overtly crowded, papillary, or closely apposed glands. Any hyperplasia associated with nuclear atypia is classified as atypical hyperplasia . Using these criteria, Kurman et al. studied a group of 170 women with untreated hyperplasia and found that the frequency of regression , persistence , and progression to carcinoma for women with simple hyperplasia was 80%, 19%, and 1% respectively. For complex hyperplasia the corresponding figures were 80%, 17% and 3%, whereas for atypical hyperplasia the figures were 60%, 17%, and 23%, respectively. In a separate study of 96 women with hyperplasia untreated for 1 to 13 years, 3% of the cases that lacked nuclear atypia progressed to carcinoma, compared with 24% of the cases that demonstrated nuclear atypia. Thus, nuclear atypia is a more reliable indicator of progression to carcinoma than architectural abnormality.
Nuclear atypia in endometrial hyperplasia also correlates with response to oral medroxyprogesterone acetate therapy. With this therapy, 80% of cases of endometrial hyperplasia lacking atypia regressed, 20% persisted, and none progressed to carcinoma. In the presence of nuclear atypia, 25% of hyperplasias regressed, 50% persisted, and 25% progressed to carcinoma.
Grossly, the hyperplastic tissue is pale brownish red or reddish and velvety in appearance rather than grayish and friable, as seen in endometrial cancer. Frozen section diagnosis is unreliable because there are too many variations from one area to another. Permanent tissue preparation is necessary to identify the variable and most significant changes.
Endometrial Response to Hormonal Therapy. The atrophic endometrium in postmenopausal women who are placed on estrogen and progestin therapy converts to weakly proliferative endometrium, resembling that seen in chronic anovulation, or hyperplastic endometrium, depending on the dosage and duration of estrogen therapy. Progestin effects including stromal edema, deciduoid reaction, and secretory glands, also develop.