Aim: Endometrial hyperplasias (EH) are precancerous lesions. They are quite often misdiagnosed in surgical pathology. For the correct diagnosis of EH, the criteria for the differential diagnosis should be determined and the causes of misdiagnosis should be eliminated. For this reason, we decided to re-evaluate the cases that we had formerly diagnosed as EH.

Material and Method: We re-evaluated 1000 cases who were diagnosed as endometrial hyperplasia in our clinic between January 1995 and April 2014 in terms of the correct diagnosis and factors which lead to misdiagnosis.

Results: During the first examination, 439 of simple hyperplasia without atypia and 61 of simple hyperplasia with atypia were found. But when they were re-evaluated, it was found that only 14 of the cases were simple hyperplasia with atypia but 47 of cases were not containing atypia. Of the 439 cases formerly diagnosed as simple EH without atypia, %31 (n=136) were evaluated as proliferative endometrium, %32 (n=140) as irregular proliferation, %0.7 (n=3) as metaplastic changes, %6.3 (n=28) as endometrial polyp, %25 (n=110) as simple EH and %5 (n=22) as insufficient. When 33 cases which were diagnosed with complex atypical hyperplasia were re-evaluated, complex atypical hyperplasia was found only in 4 cases. When atypical cases were examined evidence of invasion have been detected and diagnosed as adenocarcinoma. Of the 467 cases formerly diagnosed as complex hyperplasia without atypia, %37.7 (n=176) were evaluated as secretory endometrium, %6.6 (n=31) as proliferative endometrium, %8.6 (n=40) as endometrial polyp, %4.9 (n=23) as dysfunctional uterine bleeding, %2.4 (n=11) as Areas-Stella reaction, %4.5 (n=21) as metaplastic changes, %0.2 (n=1) as adenocarcinoma, %33 (n=154) as complex EH and %2.1 (n=10) as insufficient.

Conclusion: Inadequate sampling, technical problems and lack of experience may be assumed as the main factors causing diagnostic discordance.