Abstract
A 15-year-old, spayed female, Scottish Straight cat without any traumatic history was presented with swollen abdomen and diagnosed as an abdominal wall hernia. Abdominal ultrasound revealed thickened, irregular, and hypoechoic change of abdominal wall muscle adjacent to defect. During the herniorrhaphy, multiple nodules were identified in the subcutaneous tissue around the defect. Histological examination of the nodular tissue was performed, and it was confirmed as mammary gland tumor. After the surgery, metastatic changes of the pancreas were identified, and pleural effusion and ascites were also confirmed. The patient deteriorated rapidly and died 78 days after the surgery. This is the first case presenting abdominal wall hernia induced by malignant tumor in veterinary medicine.