Histology of the normal ovary in premenopausal patients

Detailed descriptions of ovarian histology are rare. We reviewed in detail 57 cases of normal ovaries in premenopausal patients, when the ovaries are active and primordial follicles are found. We also proposed updated definitions to more clearly distinguish inclusion cysts, which do not have a known relationship with any disease process, from endosalpingiosis, a lesion closely associated with low grade serous neoplasia of the ovary. The most interesting findings were the significant variation in the histologic features including the variation in the amount and the distribution of primordial follicles, follicular cysts, and endosalpingiosis, within the ovary and between both ovaries in the same patient, the frequent presence of primordial follicles in the medulla, specifically in cases of multiple follicular cysts, and the frequent presence of endosalpingiosis. We believe that to confirm a pathologic process in the ovary, we need to become familiar with the histologic features of the normal ovary and their variations.