The stroma immediately surrounding the follicles differentiates into plum elongated cells known as theca cells. The granulosa cells, specialized cells of probable mesonephric origin that are derived from the sex cords, surround the germinal cells that form the follicles. The germ cells, also known as oocytes, are located near the periphery of the stroma.

A dense, fibrous tissue, the stroma, which is derived from the mesenchyme, makes up most of their internal substance. A single layer of cells, the surface epithelium, which is derived from the coelomic epithelium, lines their external surface. They are suspended by peritoneal folds and ligaments on either side of the uterus and attached to the back of the broad ligament of the uterus, behind and below the uterine tubes. In the adult, the ovaries are flat, nodular, oval structures that measure between 3 and 5 cm in their greatest dimension and weigh between 2 and 4 g. The coelomic epithelium remains at the periphery, enwrapping the developing ovary. Instead, mesonephric cells and germ cells remain closely associated, forming ill-defined ovarian sex cords embedded in the primitive mesenchyme. At two months gestation, the primitive gonad is recognized as an ovary because of the lack of development of the well-defined testicular sex cords. This finding explains the origin of tumors that are commonly associated with testicular tissue but appear in the ovaries and vice versa. Ovaries and testes develop in similar fashion until approximately the fourth month of embryonic life. The different tumor types that arise in the ovary are linked to the different cell types that are present at this stage of development: coelomic epithelial, mesenchymal, mesonephric, and germ cells. Cells from adjacent transient embryonic structures, known as mesonephros, concurrently invade the mesenchyme, and the primordial germ cells arrive after a long journey that starts at their place of origin in the yolk sac and takes the cells along the distal embryonic intestine and the posterior wall of the embryonic body cavity. Continued proliferation of the coelomic epithelium into the underlying primitive connective tissue, known as the mesenchyme, leads to the formation of the primordial indifferent gonads.

1- 7 The current discussion focuses on key developmental events and anatomic features that shed light on the natural history of ovarian cancers.Īt approximately five weeks of gestation, thickenings of the lining of the posterior embryonic body cavity, the coelomic epithelium, form the genital ridges. A complete description of the embryology and anatomy of the ovary is beyond the scope of this monograph however, comprehensive reviews are available for those who seek more detail. Knowledge of the embryology and microscopic anatomy of the ovary is fundamental to the understanding of the various cancer types that originate in this organ.

Pathology cancer