A Mini Pinscher dog 8 years old with a weight of 5,8 kg, female sex. A dog have lumps in the right mammary glands of the second nipples from cranial. Dogs look healthy with good appetite and drink, normal defecation, and urination. In addition, the haematology analysing exhibited a high lymphocyte  and low MCH, MCHC and HGB. Based on x-ray examinations, the dog has an abnormality on the mammary gland. The results of the physical and histopathological examination exhibited that the dog was diagnosed with mammary gland tumor. Dogs are treated with mastectomy surgery to remove the tumor. Five days after surgery, drainage tube was released and the wound was cured.