Use of Vincristine Sulfate in the Treatment of Squamous Cell Carcinoma in a Horse's Lacrimal Gland

Abstract

Background: Squamous cell carcinoma (SCC) is one of the most common cutaneous neoplasms found in equine breeding. The main cause is still unknown, based on predisposing factors such as excessive exposure to ultraviolet rays, advanced age, depigmented skin and viral or parasitic agents. There is currently a range of possibilities for the treatment of SCC. The choice of the ideal treatment changes according to the location, evolution and size of the tumor, economic costs and availability of material. The present case report aims to report the case of a Campeiro breed, diagnosed with SCC in the left lacrimal gland region and to evaluate the action of vincristine sulfate as intralesional chemotherapy. 

Case: A 30-year-old stallion of the Campeiro perlino coat it was attended in the sector of Clinic and Surgery of Large Animals, at the Federal University of Santa Catarina - Curitibanos campus. Physical examination revealed an alert and docile temperament, with no considerable physiological changes. In the evaluation of the left eye, it was observed a mass of 2x2 cm rosacea, with granular and ulcerated appearance, it was detected in the portion of the medial corner of the eye, and the lacrimal gland cannot be macroscopically delimited. Also it was detected a moderate mucopurulent secretion. The mass was collected through fine-needle aspiration (FNA) and puncture without aspiration of contents found in the third eyelid region for cytological analysis, and a malignant epithelial cell neoplasia associated with septic suppurative inflammation was observed, suggestive of SCC. After the laboratory results analyzed, 0.25 mL of intralesional vincristine sulfate (Vincizina®) with 20x06 needle was applied in the base of the tumor mass as treatment. After 24 days of the first and only application of the antineoplastic, treatment success was remarkable, with a macroscopic involution of the tumor area up to 80%. 

Discussion: The anatomical location of SCC covering the lacrimal gland, which is an important mechanism for ocular lubrication and cleaning, has prevented surgical excision from being instituted as an alternative treatment, due to subsequent complications such as corneal dryness and possible ulcer development. Therefore, intralesional chemotherapy became a safe and effective alternative to control and delay tumor mass, preserving the functions of the lacrimal gland. Vincristine is commonly used in veterinary medicine as an antineoplastic treatment of transmissible venereal tumors with inhibitory action on tumor cell division. Previous reports demonstrated success in the use of intravenous vincristine sulfate in the treatment of animals with benign and malignant sarcoids. In the present report satisfactory results were obtained, with only one application of intralesional vincristine sulfate, probably the continuity in the administration of the drug could have propitiated results with more effectiveness. By reason of the surgical excision, treatment of choice, not be feasible in this case, the use of a new form of treatment, less invasive and effective, aims to maintain the function of the affected organ and consequently in the welfare of animal. Every successfully treated animal should be monitored so that, in case of recurrence, it is re-treated as soon as possible.