Nomenclature and Potential New Classification to Unify Endometrial Neoplasia

A dualistic model has been developed in endometrial carcinogenesis based on the clinico-pathological observations and molecular evidence, which provides a valuable framework for the study of various aspects of endometrial carcinogenesis and for the potential development of therapeutic modalities that are pathway specific.

One aspect of cancer prevention is the recognition of morphologically distinctive precursor lesions or “precancers”, so that a therapeutic intervention can be administered prior to the development of the well-developed malignancy. However, sometimes conclusions are hard to draw by comparing the so-called “precancer” related data, basically due to the problem of ever-evolving nomenclature of endometrial precancers.

Among endometrial carcinomas, endometrioid carcinoma is the most frequent and is the most extensively explored subtype, with the most various terminologies created for precursor descriptions.

We propose a nomenclatural system for the putative precursor lesions that represents an expansion of the definition of endometrial intraepithelial neoplasia (EIN) designation and which can potentially be applied to all major histologic types of endometrial neoplasms. All precursor lesions will be designated EIN but always with a prefix that identifies the histologic subtype of the invasive cancer that they are supposedly a precursor of.

In the context of endometrioid lesions, the EIN system of Mutter et al will be adopted, with a distinction been made between benign endometrial hyperplasia and strictly defined EIN; the latter will always be referred to as Endometrioid EIN.

1. In the context of serous lesions, the terms EIC or serous EIC will be discontinued; EmGD lesions will be designated serous EIN.

2. For clear cell lesions, the putative precursor lesion previously described will be referred to as Clear cell EIN. This is illustrated in the following graph:

Chart illustrating nomenclature for putative precursor lesions
Chart illustrating nomenclature for putative precursor lesions