Regional Mastectomy in Dogs

Mastectomy is the surgical removal of mammary glands in a dog that is conducted when abnormal growths or mammary masses are found. Mammary masses are common in dogs, accounting for almost half of all cancerous tumors in female dogs. Mammary masses tend to be malignant and invasive and require intervention or they are likely to become life-threatening. 

When a mammary mass or masses are locally or regionally located around one or between two mammary glands, a local or regional mastectomy may be performed to remove only the mammary gland or glands associated with that mass. This procedure is less invasive than a unilateral or bilateral mastectomy which involves the removal of all mammary glands on one or both sides, however, it may not always be as effective at preventing future disease, as remaining mammary glands are susceptible to abnormal growths. When required for the removal of mammary masses, local or regional mastectomy is performed by a veterinary surgeon under general anesthesia. The mass and associated tissue is removed to ensure that all abnormal cells are removed and prevent the spread of malignant cells.

A plan to address mammary cell masses prior to surgery will be determined by your veterinarian. Usually the least invasive method is used, which, in the case of masses located in only one or two mammary glands, is local or regional mastectomy. However, this needs to be weighed against the likelihood of cancerous spread to remaining mammary tissues. Also, if additional mammary growths are located during the surgery, the surgical plan may need to be revised to involve a unilateral or bilateral mastectomy.

Your veterinarian will advise you to fast your dog from food the night before surgery to prevent complications with general anesthesia administration. Pain killer will be administered along with general anesthetic prior to mastectomy. Once anaesthetized, your dog's mammary region will be clipped and cleaned to prevent contamination. Surgical drapes are also used to maintain a sterile surgical site. An elliptical incision is made around the mammary gland, including healthy tissue, which will also be removed to ensure adequate tissue margins around the mammary mass.

The veterinarian removes the skin, mammary tissue and underlying fat of the affected mammary gland or glands, however the rectus fascia or muscle should be left intact. This procedure is therefore not appropriate if masses are fixed to underlying muscle tissue.

The mass, mammary tissues, and healthy tissue margins are excised with a scalpel. Blood vessels are cauterized or tied off to control bleeding. Tissue removed is preserved and sent for evaluation by a veterinary pathologist. 

The surgical wound is closed using absorbable sutures to close internal gaps and the mammary skin incision is closed with sutures or staples. Drains may be placed to allow accumulated fluid in surgically created spaces to drain during healing if required. Drains are secured and held in place with bandaging and pads.

Your dog will be monitored during recovery from anesthesia and assisted as required.

Recurrence of mammary tumors in remaining mammary glands is common and subsequent surgeries may be required if only regional mastectomy is performed. For cancerous tumors, subsequent chemotherapy or radiation therapy may be used, however the effectiveness of these treatments has not been established in dogs for mammary tumors. Sarcomas are associated with shorter survival time then carcinomas. Prognosis for benign tumors is good, although recurrence can occur in other mammary glands. Prognosis of cancerous masses is more guarded, especially if the tumor has begun to spread.

Following local/regional mastectomy your dog should have activity restricted until suture removal at 10 to 14 days. Pain killer may be prescribed and should be administered as directed. An Elizabethan collar and bandaging may be required to prevent your dog from biting, licking or scratching the surgical wound. Cage confinement may be necessary, accompanied by careful supervision. Your veterinarian will provide you with information on bandage care and removal. The wound should be monitored for signs of infection, bleeding, or rupture and immediate veterinary care obtained if these occur. If a drain is left in place it will have to be observed and maintained to keep it clean and unblocked and ensure it remains in place until your veterinarian removes it.

Following recovery, you will need to have regular veterinary follow-ups to look for signs of recurrence or spread of mammary masses. Radiographs may be performed as part of this follow-upp. 

The cost of local/regional mastectomy varies depending on the cost of living in your area and ranges from $200 to $500 including anesthetic and procedure.

Complications post-mastectomy include wound dehiscence, infection, hemorrhage, and interference with the wound by your pet. Careful monitoring of the wound post-surgery will decrease the likelihood of these conditions becoming life-threatening. There is a high recurrence rate with mammary tumors, and more invasive surgery may be opted for in spite of localization of current masses.

Spaying of your female dog when young, prior to their first heat cycle, drastically reduces the frequency of mammary tumors occurring. In addition, minimizing obesity and treatment with hormone drugs in intact bitches will decrease the likelihood of mammary tumors occurring.