Summary Although several studies have addressed different aspects of mucinous neoplasms arising in the ovary, such as their clinicopathologic features, immunohistochemical profile, and molecular characteristics, no study has presented an analysis of the ovarian tissue where these neoplasms arise. In this study, we included 196 cases of intestinal-type ovarian mucinous neoplasms in premenopausal patients. Our main goal was to perform a rigorous examination of the ovarian tissue surrounding these neoplasms. We also reviewed the clinicopathologic features of these cases. For comparison, the background ovarian tissue in 85 cases of ovarian serous neoplasm and in 29 cases of metastatic neoplasms to the ovary, as well as 57 normal ovaries, was examined. All the patients in this study, which included those with mucinous and with serous neoplasms primary in the ovary, those with metastatic tumors to the ovaries, and those with normal ovaries, were also premenopausal. Patients affected by ovarian mucinous neoplasms ranged in age from 13 to 52 years (median = 36 years). Nulligravidity was seen in 50%, 32%, and 22% of patients with mucinous carcinomas, mucinous borderline neoplasms, and mucinous cystadenomas, respectively. Ovarian mucinous intestinal neoplasms arise in abnormal ovaries characterized by two important features: (1) an abnormal ovarian cortex, seen in 95% of the cases, which is hypocellular or with no distinction between the cellular cortex and medulla, and (2) a remarkable paucity of primordial follicles. The abnormalities detected in the background ovarian tissue might provide insights into the tumorigenesis of these neoplasms and might facilitate their distinction from metastasis to the ovary, in premenopausal patients.