Evaluation of Immune Infiltrates in Ovarian Endometriosis and Endometriosis-Associated Ovarian Cancer: Relationship with Histological and Clinical Features

Background: the association between ovarian endometriosis (OE) and endometriosis-associated ovarian cancer (EAOC) is extensively documented, and misfunction of the immune system might be involved. The primary objective of this study was to identify and compare the spatial distribution of tumour-infiltrating lymphocytes (TILs) and tumour-associated macrophages (TAMs) in OE and EAOC. Secondary objectives included the analysis of the relationship between immunosuppressive populations and T-cell exhaustion markers in both groups. Methods: TILs (CD3, CD4, and CD8) and macrophages (CD163) were assessed by immunochemistry. Exhaustion markers (PD-1, TIM3, CD39, and FOXP3) and their relationship with tumour-associated macrophages (CD163) were assessed by immunofluorescence on paraffin-embedded samples from n = 43 OE and n = 54 EAOC patients. Results: we observed a predominantly intraepithelial CD3+ distribution in OE but both an intraepithelial and stromal pattern in EAOC (p < 0.001). TILs were more abundant in OE (p < 0.001), but higher TILs significantly correlated with a longer overall survival and disease-free survival in EAOC (p < 0.05). CD39 and FOXP3 significantly correlated with each other and CD163 (p < 0.05) at the epithelial level in moderate/intense CD4 EAOC, whereas in moderate/intense CD8+, PD-1+ and TIM3+ significantly correlated (p = 0.009). Finally, T-cell exhaustion markers FOXP3-CD39 were decreased and PD-1-TIM3 were significantly increased in EAOC (p < 0.05). Conclusions: the dysregulation of TILs, TAMs, and T-cell exhaustion might play a role in the malignization of OE to EAOC.