The molecule PAX8 could serve as a sensitive and specific biomarker of extragenital endometriosis in clinical practice, a study suggests.
The study, “PAX8: A Highly Sensitive Marker for the Glands in Extragenital Endometriosis,” was published in Reproductive Sciences.
Endometriosis is characterized by endometrial (from the womb) tissue growing outside of the uterus, usually in the peritoneum (the membrane that lines the abdominal cavity) and ovaries. However, endometriosis also can appear in the bowel, bladder, intestine, and other organs, such as the lungs and diaphragm, that are not near the reproductive system. This is classified as extragenital endometriosis.
When diagnosis is unclear, doctors use different markers such as CD10 (a molecule expressed at the surface the connective tissue cells of the endometrium) and estrogen and progesterone receptors to diagnose endometriosis.
However, these markers often are unreliable to diagnose extragenital endometriosis because the lesions in these organs have few connective tissue cells and many epithelial cells (cells that line the surface of the organs) that are not recognized by the markers.
That is why a specific marker able to recognize endometrial epithelial cells and distinguish them from other types of epithelial cells would significantly increase the reliability of the diagnosis for extragenital endometriosis.
PAX8 is a molecule essential for the development of the endometrium that serves as a specific marker for epithelial cells in ovarian and endometrium tumors. In this study, researchers evaluated if PAX8 acted as a marker for extragenital endometriosis.
They evaluated the endometrial tissue that was surgically removed from 55 patients. Eight had ovarian endometriosis (endometriomas), and 47 had extragenital endometriosis (20 in the intestine, 10 in the bladder, three in the ureteres (the tubes that propel urine from the kidneys to the bladder), three in the groin (inguinal), and 11 in the diaphragm).
The average age at surgery was 36 years for the ovarian and 37.9 years for the extragenital endometriosis group. All samples were tested for the presence of PAX8, CD10, and estrogen and progesterone receptors.
PAX8 was detected in 95.7% (45/47) of extragenital endometriosis samples and all the ovarian endometriosis samples; it was present in the endometrium-like epithelial cells, but not in the connective tissues or other epithelial cells, such as intestinal epithelial cells.
CD10 was present in 97.9% (46/47) of extragenital endometrioses and all ovarian endometriosis samples. However, epithelial cells were negative for this marker.
Among the 47 patients with extragenital endometriosis, 26 took hormones before the surgery, whereas 21 patients did not. There was no significant difference in the presence of PAX8, CD10, and progesterone receptor between those who took hormones and those who did not. However, patients who took hormones had significantly less estrogen receptor.
“PAX8 may be a useful, sensitive marker for endometriotic epithelial cells, which is not affected by hormonal therapy. This is also the first report that comprehensively examined [presence of markers in] extragenital endometriosis,” the authors stated.
Although further studies testing the applicability of PAX8 as a marker of other types of extragenital endometriosis such as umbilical and abdominal should be performed, the authors concluded that “PAX8 is a highly sensitive epithelial marker for extragenital endometriosis. PAX8 expression can be useful in detecting extragenital endometriosis in clinical practice.”