[A case of highly atypical hyperplasia--difficult to differentiate from carcinoma].

We present a 51-year-old nulliparous woman with highly atypical hyperplasia of the uterus induced by the prolonged use of exogenous estrogen. The patient was given nearly 1,415 mg of estradiol dipropionate intramuscularly for over 23 years after operation for bilateral ovarian cysts. She complained of vaginal bleeding and diagnostic endometrial curettage revealed highly atypical hyperplasia which was difficult to differentiate from well differentiated adenocarcinoma. On hysterectomy, atypical tissues were limited to the upper part of the posterior wall of the uterus with no muscle invasion.