The need for a universal classification of endometriosis


Research in the Journal of Minimally Invasive Gynecology also concluded that most classification/staging systems show little or no correlation with patient outcomes.

The search, which was limited to PubMed and MEDLINE, and English-language studies published from their inception in 1966 to August 2020, included 70 studies that described a classification, staging, or reporting system in endometriosis (n= 24) or rated 1 (n = 46). A total of 22 endometriosis classification, staging and reporting systems were evaluated.1

Studies have highlighted a gap between the intended purpose and the assessed purpose. There is also a general lack of validation data confirming a correlation between pain symptoms or quality of life with any of the current systems.

However, some studies confirm the interest of the Enzian system for the surgical description of deep endometriosis. Additionally, the Endometriosis Fertility Index (EFI) has been validated to predict the likelihood of natural conception after surgery. However, the EFI system requires further evaluation of the importance of different parameters and whether to include the entire surgical treatment.

The revised American Society for Reproductive Medicine (rASRM) system has also been evaluated, but often with negative conclusions.

Apart from rASRM, Enzian, and EFI, only 2 other staging systems have been evaluated for their purpose: the Ultrasound-Based Endometriosis Staging System (UBESS) and extent of disease, complaints, objectives (ECO).

“This overview of existing systems is a first step towards a universally accepted classification of endometriosis,” wrote the authors, who acknowledged that endometriosis is a difficult disease to classify because it has phenotypes and presentations different for the type of lesions and their location. The disease also exhibits various symptoms with no clear link to phenotype or presentation.

Additionally, the natural progression of endometriosis is unknown.

Despite these obstacles, there appears to be a need for a validated classification or descriptive system of endometriosis to support further progress in defining subgroups. More important, however, is that such a system could guide treatment options for women with pain and/or infertility.

System compliance would also aid endometriosis research by unifying patient subgroups and improving the development of prognostic and predictive tools.

“Grading and staging systems are widely used in medicine and have proven useful in guiding clinical management,” the authors wrote, including the American Joint Committee on Cancer tumor-node-metastasis (TNM) staging systems for cancer, which was developed in the early 1950s to guide the clinical classification of cancer cases by anatomical extent.

The TNM system, which is revised every 6 to 8 years, is now in its eighth edition and includes staging or summary classification related to prognosis and used for treatment planning.

The TNM system has also been increasingly supplemented with molecular marker data that more accurately stratifies risk in patients and guides appropriate treatment options.

The longevity and update systems applied to TNM staging, along with the further identification of molecular subtypes, are likely important guides for the design of future endometriosis grading and staging systems that are in development. correlation with patient-relevant outcomes, according to the authors.

Meanwhile, the objective and purpose of published classification, staging, or reporting systems for endometriosis are often overlooked when evaluating classification or staging systems, thus limiting the value of assessment studies. and systems in general, according to the authors.


  1. Vermeulen N, Abrao MS, Einarsson JI, et al. Classification, staging and reporting systems of endometriosis: a review on the way to a universally accepted classification of endometriosis. J Minimally Invasive Gynecol. 2021. 28(11):1822-1848. doi:org/10.1016/j..jmig.2021.07.023

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