It should be emphasized that the reports on associated carcinomas in hysterectomy specimens relate only to atypical hyperplasias, but the distinction between complex hyperplasia and atypical complex hyperplasia has been shown to be difficult enough that one must assume that even a lesion diagnosed as complex hyperplasia without atypia might harbor a carcinoma in the subsequent hysterectomy specimen.
Based in part on the study by Kurman et al, as well as others reporting similar data in usually smaller series of cases, the assumption was made that those lesions showing cytologic atypia (atypical hyperplasias), particularly when combined with a complex architectural appearance (complex atypical hyperplasia or atypical complex hyperplasia), were those most likely to progress to endometrial adenocarcinoma if untreated.
Also beginning in the 1980s, however, publications have appeared that challenged this concept on the basis of 2 types of observations: (1) atypical complex hyperplasia has been reported to be a poorly reproducible diagnosis, with experts differing in significant proportions of cases not only with referring pathologists but also with each other (24,58,59); and (2) carcinoma can be found in uteri removed within 1 or 2 months after the diagnosis of atypical hyperplasia in a significant proportion of cases, making it unclear whether those carcinomas diagnosed many years later really represent progression or merely persistence.
Two main candidates have merged as potential replacements for atypical complex hyperplasia and associated terms.