An algorithm for endometrial meta- and hyperplasia

As to to their frequency and variety, endometrial meta- and hyperplasias ar e the most impressive examples of the growth and differentiation potential of the Muellerian system and the inductive power of steroid hormons and rel ated inter-and intracellular factors. Characteristic steroid reactions a re the glandular hyperplasias, ciliated and squamous cell metaplasias in the case of hyperestrogenism,and the mucinous and clear cell meta- and hyperpla sias in the case of gestagen excess. In 1994, the WHO established a new cla ssification of endometrial hyperplasias. This classification takes into acc ount the profound differences in cancer risk, and accordingly demands a cle arcut distinction between simple and complex (steroid sensitive, almost alw ays reversible) hyperplasias without atypia, and simple and complex (partia l steroid resistent and potential progressive) hyperplasias with atypia. Th e conclusion drawn from clinical experience is, that the atypical endometri al hyperplasia-and this alone-is the precancerous lesion of the ordinary en dometroid carcinoma. In contrast, it is still not clear which biological si gnificance accounts to all the complex squamous, mucinous, clear cell and c iliated cell meta- and hyperplasias. Yet, it is good pathological and clini cal practice, to upgrade any metaplastic lesion with nuclear atypia, a nd t o remove the uterus as it is done in almost all atypical endometrial hyperp lasias.