Clinicopathological correlations of peritoneal endometriosis and deep infiltrating endometriosis

The present study aims to investigate the clinical and histopathological features of peritoneal endometriosis (PEM) and deep infiltrating endometriosis (DIE).

A total of 100 patients with PEM and DIE admitted to Dalian Women and Children's Hospital/Dalian Women and Children's Medical Center between October 2018 and December 2021 were selected as the study subjects. One hundred and thirty-one PEM specimens and 37 DIE were collected, 22 cases of these patients' eutopic endometrium were used as control (15 in PEM, seven in DIE). The present study mainly analysed the pelvic distribution, the histopathological and immunohistochemical features and peritoneal invasion of PEM and DIE.

The main distribution of PEM and DIE was located in the posterior pelvic cavity (p < .001). The histopathological characteristics of different PEM forms were different: the contents of endometrioid glands, endometrioid stroma, smooth muscle, fibrous tissue and blood vessels in different lesions were statistically significant (all p < .050). Estrogen receptor (ER) of PEM and DIE was highly expressed in endometrioid glandular epithelium and endometrioid stroma, without statistical significance (p = .330/.113). Progesterone receptor (PR) was also highly expressed in endometrioid glandular epithelium and endometrioid stroma without statistical significance (p = .757/.798). Ki-67 expression of DIE in endometrioid glandular epithelium was significantly higher than that in brown and white lesions (p < .001), while its expression in the endometrioid stroma was not statistically significant in red lesions (p = .070), but higher than that in other PEM lesions (p < .001). Different morphological lesions had different invasiveness rates and depths of invasion to the peritoneum. White lesions had a deeper subperitoneal invasion level than transparent and vesicular lesions.

Although different morphological appearance of PEM is a degenerative process, some active brown lesions of PEM have invasive effects during the process and may further develop into DIE. PEM and DIE may be different developmental stages of the same disease.