Vaginal Squamous Cell Carcinoma in a Nelore cow

Abstract

Background: Skin tumors are the most common neoplasia in veterinary medicine and squamous cell carcinoma (SCC) is the most frequent. In cattle, it is the main tumor besides linfosarcoma and normally affects taurine cattle, but is rare in Nelore cattle. SCC mainly affects mucocutaneous junctions such as the eyelids, sclera, vulva, and perineum, and has already been described in vaginal, eye, and periocular tissues, in addition to the superior digestive tract. The purpose of this paper is to describe a vaginal squamous cell carcinoma in a Nelore cow.

Case: A 10-year-old Nelore cow, used as an embryo donor, was submitted to a necropsy procedure. Clinically, the animal had prolonged recumbency, anorexia, weight loss, and vaginal discharge. There was a history of recurrent vaginal prolapses and an intraluminal vaginal mass that had grown over two years. At necropsy, there was diffuse fibrinous peritonitis with marked intestinal adhesions; the vagina was markedly expanded and measured 40 × 20 cm due to the presence of an intraluminal mass occupying the vestibulum and extending up to the cervix. In the vaginal lumen, there was large amount of fibrinonecrotizing malodorous material; the vaginal wall was thickened by an unencapsulated and poorly delimited, firm and white mass composed of sheets and nests of epithelial cells from the squamous layer surrounded by abundant fibrovascular stroma. The neoplastic cells were polygonal with marked pleomorphism, anisokariosis, and anisocytosis; abundant; eosinophilic; and had well-defined cytoplasmic borders. Sometimes it was possible to see desmosomes. The nuclei were rounded to oval with sparse chromatin and one or more nucleoli were seen. Mitotic figures were frequent (at least 3 per higher power field) and there were also a few multinucleated cells. Frequently, there was the formation of distinct keratin “pearls”.

Discussion: SCC frequently occurs in the skin, eyes, and vulva in cattle, since these are sites that lack pigment within the epidermis and have prolonged exposed to ultraviolet light. Vaginal SCC has already been described in one cow with recurrent vaginal prolapses that was submitted to follicular aspiration. In a survey of cattle tumors, most genital tract neoplasias affected the uterus, and vaginal tumors normally originated from connective tissue - fibromas, fibropapillomas, and fibrosarcoma - or muscular tissue - leiomyoma and leiomyosarcoma. Irreversible changes in cellular DNA can occur due to physical or chemical carcinogens, and also chronic inflammation. The cow in this paper was frequently submitted to follicular aspiration and this can cause chronic inflammation in the vaginal mucosa after the puncture and, when it’s chronic, can represent one of the main initiating factors for tumor development. This cow’s death was caused by diffuse and marked peritonitis. The same cause was previously described in cows submitted to follicular aspiration and, in one of these animals, there was a rectal perforation caused by mistakes during the procedure. In this animal, we did not find any lesions in the rectum or intestines, however, considering the gravity of the peritonitis, we were not able to exclude this hypothesis. Papillomavirus has previously been found in SCC in sheep and probably acts synergistically with ultraviolet light, however, in this animal, we did not test for the virus. Squamous cell carcinoma in an uncommon tumor in cows’ vaginas, however, this should be included as a possible differential diagnosis, especially in animals submitted to situations that can cause chronic inflammation in the genital tract.