This is a single center prospective observational study to characterize the immune landscape of newly diagnosed epithelial ovarian cancer (OC). Patients with newly diagnosed epithelial OC will be enrolled in 4 different cohorts: A) Newly diagnosed high grade serous or endometroid OC undergoing primary debulking surgery; B) Newly diagnosed high grade serous or endometroid OC undergoing neoadjuvant chemotherapy (NACT) followed by interval debulking surgery; C) Rare subtypes of epithelial OC (low grade serous, low grade endometrioid, clear cell, mucinous or carcinosarcoma) undergoing primary debulking surgery; D) Rare subtypes of epithelial OC (low grade serous, low grade endometrioid, clear cell, mucinous or carcinosarcoma) undergoing NACT followed by interval debulking surgery. A cohort of women undergoing adnexectomy for benign pathology will be enrolled (cohort E) for comparative analysis. Enrolled patients will be asked to provide the following biological samples at specified time points: archival and fresh tumor tissue, peripheral blood samples, rectal and vaginal swabs, ascites (when present). The main aim of the study is to characterize the immune landscape of epithelial OC in tumor tissue and peripheral blood and correlate the presence of myeloid-derived suppressive cells (MDSCs) and other immune infiltrates and of the systemic immune response with progression free interval (PFI) in epithelial OC.