Explanation

• Mast cells form mast-cell tumors. A dog's immune system contains mast cells as part of his body's normal defense mechanism. Mast cells contain enzymes that naturally break down protein as well as eliminate parasites and bacteria in the body. Tumors form when mast cells group together and release large amounts of enzymes. This causes harmful effects to the dog's regular bodily functions, including his heart rate and blood pressure. Stage-II tumors generally involve one or more of the dog's lymph nodes.
  
  

Occurrence

• Mast-cell stage-II tumors occur in dogs of any age and breed. However, this form of canine cancer usually shows up in dogs over the age of eight. It appears more frequently in certain breeds, such as Boston Terriers, Boxers and Golden Retrievers. It's also common in dog breeds with heads that are short and wide.
  
  

Cause

• Heredity, the environment and a virus all have been implicated as the cause of mast-cell tumors. The exact cause remains under debate. Little study has been completed on the tumor's origin compared with other types of cancers present in humans and animals, as mast-cell tumors aren't found in humans.
  
  

Early Stages of Diagnosis

• While stage I offers the best prognosis, stage II provides the second-best. A biopsy confirms the tumor type. A stage-I tumor shows little sign of spreading. Stage-II tumors demonstrate malignancy and characteristics that make response to treatment less predictable.
  
  

Stage-II Prognosis

• The outlook for recovery is good for dogs with stage-II tumors. When the tumor is on the dog's legs, the prognosis is usually even better. Surgically removing the mast-cell tumor and surrounding tissue is generally the best treatment option for this tumor stage. Radiation also decreases the chance that the tumor will come back. Certain anticancer drugs are effective in treating stage-II tumors.