Which cell defines endometriosis?

What are the initial cellular characteristics of endometriosis?

Key Points

Highlights:

• This article aims to highlight characteristics that underline the initial, histologic identity of endometriotic lesions.

Key Results:

• Endometriosis is a highly variable disease characterized by many symptoms and cellular components.
• The phenotype may vary with age groups, localization of the lesion, clinical presentation; resulting in a spectrum. 
• Endometriosis should be characterized initially by one common feature: the presence of epithelial cells and stroma, and active neo-angiogenesis.
• Muscular metaplasia, fibrosis, and the disappearance of endometrial cells and stroma should not be used as an initial characterization to define endometriosis.

What’s done here?

• Authors describe their thought in response to a previous article that enhances the importance of the consistent presence of fibrosis and myofibroblasts in
  endometriotic lesions and their crucial role in the pathogenesis of the disease (by Vigano et al)
• Authors present their thoughts and reflections on the claim that glandular epithelium from endometrial lesions is not surrounded by stroma and that no epithelium can be found in the wall of these ovarian endometriomas.

Limitations:

• This article is a response to a claim made by an opinion paper.

Lay Summary

A well-accepted theory regarding the pathogenesis of endometriosis hypothesizes that the origin of endometriosis is from peritoneal dissemination of endometrial cells and stroma during the neonatal period or menarche.

Varying cellular components of endometriosis have been observed in the setting of different clinical conditions such as adolescent versus adult endometriosis. Additionally, the phenotype of endometriosis varies with its localization. For example, deep endometriosis tends to involve the pouch of Douglas (recto-uterine pouch) and uterosacral ligaments and occasionally contains a fibrotic-muscular component.

Infertility in patients with endometriosis is often associated with peritoneal adhesions and ovarian endometrioma formation preceded by bleeding of superficial implants. Patients taking hormonal replacement therapy who also have endometriosis may experience a return of pain symptoms and are at low risk of developing malignancy due to malignant transformation of endometriotic nests.

Endometriosis is a highly variable disease that presents itself clinically in many forms and histologically with varying cellular components.

Brosens et al.,  highlight that muscular metaplasia, fibrosis, and disappearance of endometrial cells and stroma should not be the initial, common feature that defines endometriosis, in their recent paper appeared in Human Reproduction.

"Given the spectrum of different phenotypes, there is only one feature that initially common to all variants: the presence of epithelial cells, stroma, and an active neo-angiogenesis. Therefore, these features should be an integral part of any definition of endometriosis", the authors conclude.  

Research Source: https://www.ncbi.nlm.nih.gov/pubmed/29420768