Bilateral ovarian cysts originating from rete ovarii in an African green monkey (Cercopithecus aethiops)

Rediscovering the Rete Ovarii: a secreting auxiliary structure to the ovary

The rete ovarii (RO) is an appendage of the ovary that has been given little attention. Although the RO appears in drawings of the ovary in early versions of Gray's Anatomy, it disappeared from recent textbooks, and is often dismissed as a functionless vestige in the adult ovary. Using PAX8 immunostaining and confocal microscopy, we characterized the fetal development of the RO in the context of the ovary. The RO consists of three distinct regions that persist in adult life, the intraovarian rete (IOR), the extraovarian rete (EOR), and the connecting rete (CR). While the cells of the IOR appear to form solid cords within the ovary, the EOR rapidly develops into a convoluted tubular epithelium ending in a distal dilated tip. Cells of the EOR are ciliated and exhibit cellular trafficking capabilities. The CR, connecting the EOR to the IOR, gradually acquires tubular epithelial characteristics by birth. Using microinjections into the distal dilated tip of the EOR, we found that luminal contents flow towards the ovary. Mass spectrometry revealed that the EOR lumen contains secreted proteins potentially important for ovarian function. We show that the cells of the EOR are closely associated with vasculature and macrophages, and are contacted by neuronal projections, consistent with a role as a sensory appendage of the ovary. The direct proximity of the RO to the ovary and its integration with the extraovarian landscape suggest that it plays an important role in ovary development and homeostasis.

Cystic rete ovarii and uterine tube adenoma in a rabbit

A 6-year-old female rabbit was presented to a veterinary clinic, and the result of ultrasound examination suggested a tumor in the uterine tube. Subsequently, both ovaries and uterus were surgically removed. In gross, a single large cyst in the right ovary and enlargement of the left uterine tube were observed. Histological examination revealed that the cyst had developed in the hilus of the ovary and was lined by single-layered cuboidal cells. In the left uterine tube, a tumor composed of epithelial cells arranged in tubular structures and pleomorphic cells between the tubular structures was observed. Immunohistochemically, the epithelial cells of the cyst were positive for pan-cytokeratin, cytokeratin 18, CD10, E-cadherin, calretinin and estrogen receptor; the tumor cells of the left uterine tube were positive for pan-cytokeratin, cytokeratin 18, E-cadherin, vimentin, calretinin and estrogen receptor. From these results, the cyst was diagnosed as cystic rete ovarii, and the tumor was diagnosed as adenoma of the uterine tube. This case is the first to demonstrate cystic rete ovarii and uterine tube adenoma in rabbits.