How to recognize and diagnose mast cell tumors in dogs

Abstract

Mast cell tumour is one of the most common cutaneous neoplasms in dogs, ranging from well differentiated to aggressive tumors with metastases. Currently, prognosis and therapeutic definitions of canine cutaneous MCTs are based on the histological grade of malignancy. Clinical examination and treatment were performed in Dnipro veterinary clinics and pathological analysis in the Department of Animal Anatomy, Histology and Pathomorphology, Dnipro State Agrarian and Economic University (Dnipro, Ukraine). Thirty-six dogs with a history of skin neoplasia were examined. Skin MCTs were diagnosed in 23 males and 13 females, aged between 5 and 15 years. No breed predisposition was found out in tested cohort. MCTs were located on the trunk (44.4%), limbs (33.4%) and less frequently on the head and neck, axillary, inguinal and perineal areas (22.2%). MCT was detected in 8 animals where the malignancy was systemic and develops metastatic spread to internal organs. Pathological diagnosis included cytopathological examination of tumor material, pathological analysis of samples obtained by incisional biopsy using haematoxylin/eosin and toluidine blue staining. According to the diagnostic criteria (smear cellularity, presence of cells with basophilic cytoplasmic granularity, size and number of cytoplasmic granules, presence or absence of mitotic figures, nuclear pleomorphism, presence or absence of binucleations or multinucleations, anisokaryosis), benign mast cell tumour (high grade) was diagnosed in 23 animals and malignant mast cell tumour (low grade) in 13 animals. These results were confirmed by histopathological methods using haematoxylin and eosin staining. Additional staining of histological sections with toluidine blue allowed differentiation of benign mast cell tumours into high-grade (38.9%) and intermediate-grade (5%).