Canine Mast Cell Tumor: Molecular Pathogenesis and Diagnostic Advancement

Mast cell tumor is the second-most frequent malignant neoplasm in dogs, after mammary gland tumors. Overall prevalence rate of mast cell tumor is up to 0.27% of the total dog population and representing up to 21% of all cutaneous tumors in dogs. Mast cells were first discovered by Paul Ehrlich in the year 1878. Mast cells are widely distributed in connective tissues throughout the body. Biological behaviour of tumors is highly unpredictable and majority were found as solitary nodules in the skin. Middle-aged to older dogs are highly susceptible however no sex predisposition has been revealed. Tumor varies in shape, size and consistency according to its anatomical site and nature of tumor. In most of the cases, activating c-KIT mutations and aberrant KIT expression are leading cause of mast cell tumors. Ultimately, transphosphorylation of the KIT receptors activates of abnormal proliferation of mast cells. Diagnosis of mast tumors involves cytology, histopathlogy, special staining, and immunohistochemistry.