Proliferation activity with PCNA and Ki-67 in endometrial hyperplasia and endometrial adenocarcinoma Because of the relationship between endometrial hyperplasia and adenocarcinoma and the diagnostic difficulties, on some occasions, the subject has been popular for long time. In order to perform the diferantial diagnosis of atypical hyperplasia and well-differentiated adenocarcinoma and to estimate the relationship between the other parameters by means of prognosis Ki-67 and PCNA have been assayed in many studies . Ten complex hyperplasia without atypia, 7 complex hyperplasia with atypia and 10 endometrial adenocarcinoma cases have been evaluated by immunohistochemically with Ki-67 and PCNA. Positivity with PCNA in one of the hyperplasia cases without atypia and in one of the hyperplasia cases with atypia have been detected. In one case of complex hyperplasia with atypia Ki-67 was positive. Among the adenocarcinoma cases, 8 out of 10 cases have been positively stained with PCNA and 5 cases have been noted to be positive with Ki-67. The distinction between complex hyperplasia with atypia and adenocarcinoma cases by means of expression of PCNA and Ki-67 was significant.