Mast cell tumours, a common canine cancer, can arise in any skin area besides the dog's paws. Often hard to identify, mast cell tumours vary in size, shape and even colour. On a dog's paw, the tumour often appears as a hard, round nodule or an ulcerated open sore. The dog usually appears to show no pain when a person handles the nodule.
Dogs normally suffer from mast cell tumours after the age of eight. The cause of the tumour is unknown, although speculation exists that the cause may be a virus, according to Doctors Foster and Smith Pet Education.com. A genetic prevalence appears to exist for mast cell tumours. Certain breeds such as the boxer, English bulldog, golden retriever, cocker spaniel and schnauzer are at increased risk, according to Mar Vista Animal Medical Center. Humans do not get mast cell cancer.
Dogs that suffer from a mast cell tumour often exhibit symptoms that the owner will not recognise as being related because the tumour releases toxins into the dog's system which causes it to vomit, suffer diarrhoea with blood, lethargy, blood clotting issues and a feeling of being unwell. When stimulated by pressure the mast cells release histamines, serotonin, proteolytic enzymes, heparin and prostaglandin into the body in toxic excess, which causes the dog to suffer a variety of symptoms that appear to be unrelated to the tumour on the dog's paw. The location of the mast cell tumour on the dogs paw often means that the tumour is continuously stimulated, making the dog appear quite ill.
The veterinarian will possibly take a biopsy of the paw tumour and will order several blood tests to help detect the chemicals the mast cells release. Once the veterinarian is reasonably sure the dog has a paw mast cell tumour, he will order further tests such as CAT scans and ultrasounds to determine if the cancer has spread beyond the dog's paw.
Prompt surgical removal of the infected area is the first step in treatment. Further treatment may include localised radiation and systemic chemotherapy if the cancer is aggressive or has metastasised to other areas of the body. Veterinarians often prescribe prednisone for treatment by itself or with a combination of other chemotherapy drugs such as mitoxantrone, L-asparaginase, vinblastine, vincristine, cyclophosphamide or doxorubicin.
Dogs with complete surgical resection of the tumour have a promising prognosis. Mast cell tumours that are widespread and aggressive rarely respond well to surgery, radiation or chemotherapy. Tumours that arise in the dog's paw nail bed tend to be extremely aggressive, according to Mar Vista Animal Medical Center.