Squamous metaplasia of the rete ovarii in a Zebu cow

Stratified keratinizing squamous epithelium in the ovary has been associated with the diagnosis of ovarian teratoma in cows. Recently, the diagnosis of "epidermoid cyst" has been proposed. A case of squamous metaplasia of the rete ovarii in a Zebu cow is described in this report. A crossbreed Zebu cow had both ovaries enlarged with multiple cysts. Most cysts were lined by well differentiated keratinizing stratified squamous epithelium and filled with keratinized lamellar material. Some cysts were lined by an epithelial layer that ranged from single cuboidal, double cuboidal epithelium, stratified non keratinized epithelium, and areas of keratinizing stratified squamous epithelium. Single or double layered cuboidal epithelia of the cysts expressed low molecular weight cytokeratin 7, whose expression was absent in the keratinizing stratified squamous epithelia of same cysts. Conversely, high molecular weight cytokeratins 1, 5, 10, and 14 were strongly expressed by the keratinizing stratified epithelium. Squamous metaplasia of the rete ovarii was diagnosed. Squamous metaplasia of the rete ovarii, may account for some of the previously described squamous lesions in the ovary, which may have been misinterpreted as teratoma or epidermoid cysts.