Malignant Neoplasms in Cats - Epidemiological Surveillance in a Veterinary Teaching Hospital's Oncology Service

Background: Cancer is a leading cause of death in dogs and cats, with its high prevalence linked to factors such as population growth, advances in veterinary medicine, and increased life expectancy. In Brazil, which had the 2nd largest pet population globally in 2017, the feline population is expanding rapidly and is expected to surpass dogs within a decade due to urbanization and lifestyle changes. Cancer epidemiology allows for the analysis of disease distribution, risk factors, and the impact of prevention and treatment on survival and quality of life. This study aims to conduct an epidemiological survey of feline oncology cases at the FCAV/UNESP Veterinary Hospital from 1997 to 2018. Materials, Methods & Results: This retrospective study analyzed 21 years of feline malignant neoplasms at a veterinary hospital. Data from medical records included patient characteristics, clinical history, diagnostics, treatments, and outcomes. Ethics approval was unnecessary, and owner consent was obtained. Medical records identified 70 cases of feline malignant neoplasms with adequate information. Epithelial tumors were the most prevalent (71.43%), with squamous cell carcinoma being the most common (72%), followed by mesenchymal neoplasms (18.57%) and round cell tumors (8.57%). Most affected patients were female (66%), predominantly aged between 7 and 14 years. Light-skinned bicolor cats were the most affected (34%), and 28% had outdoor access. Single lesions were the most frequent (42%), and 12% of tumors were smaller than 1 cm. Ulcerated tumors were observed in 30% of cases. The most affected regions included the mammary chain (26%), periocular areas (20%), and nasal planum (20%). Among treatment approaches, 78% of cats received therapy, with surgery, chemotherapy, cryosurgery, and electrochemotherapy being the most commonly used modalities. Mesenchymal tumors exclusively affected females, primarily in the subcutaneous tissue of the lateral abdomen (46.15%). Surgery was the primary treatment, followed by chemotherapy. Round cell neoplasms included lymphomas and mast cell tumors, mostly affecting the gastrointestinal tract and skin. Surgery and chemotherapy were the main treatment options, with 1 case surviving beyond 24 months. Squamous cell carcinoma was associated with sun exposure and light skin, characterized by ulcerated and invasive lesions. Injection-site sarcomas were predominantly found in vaccinated cats, confirming their association with injectable substances. Discussion: Squamous cell carcinoma (SCC) was the most common epithelial tumor, affecting outdoor cats with light skin and sparse fur, mainly in sun-exposed areas. Lesions were often ulcerated, adherent to muscle, and invasive to bone. Surgery, chemotherapy, cryosurgery, and electrochemotherapy were the main treatments, as radiotherapy and photodynamic therapy were unavailable locally. Feline injection-site sarcomas (FISS) predominantly affected vaccinated and neutered cats aged 7-10 years, consistent with literature. Tumors were mostly in subcutaneous tissue, showing infiltrative behavior. Surgical excision was the primary treatment, with histological subtypes including sarcomas and fibrous histiocytomas. Chemotherapy involved doxorubicin alone or combined with other agents. Lymphomas were the most frequent round cell tumors, with gastrointestinal and cutaneous forms observed. A senior cat with cutaneous lymphoma exhibited metastases, resembling cases in literature. Treatment included lomustine and prednisolone. The growing cat population in Brazil as well as around the world, brings a crescent need for further medical knowledge about the incidence of neoplastic processes in felines. Keywords: cancer, tumors, oncology, neoplasms, neoplastic process, feline.