Surgery is usually the treatment of choice for tumours that are localized to one area and can be removed entirely without significantly compromising the patient.

The goal of surgery is to obtain wide enough margins in all directions surrounding the tumour to make sure that the entirety of the cancer tissue has been removed. Depending on the tumour type, wider margins can be necessary: the more aggressive the tumour or the more it infiltrates the surrounding tissues, the wider the margins need to be.

The 3 tumours are surrounded by the small circle, the large circle indicates the margin needed to completely remove the tumour

The patient is anesthetized prior to the surgical excision of the tumour. The goal of surgery is to remove all the cancerous tissue. However, this is sometimes not possible and as a result cancer tissue remains necessitating additional treatment. Theoretically, debulking a tumour would make it more sensitive to other therapies such as chemotherapy, radiation and immunotherapy.

Tumours that have recurred are generally harder to remove because the first surgery may deform the tissue allowing the tumour to spread more widely in the surrounding tissue.

All excised tumuors should be examined histopathologically for 2 reasons: to identify the tumour type and to ensure that the tumour has been removed completely.

• It is important to know the tumour stage and type to determine what the next steps might be: is the problem completely solved e.g. in the case of a benign tumour, or is it a malignant tumour with a high chance of recurrence.
• Recognizing the correct tumour type allows us to decide whether additional treatment (such as chemotherapy, radiation, immunotherapy) is possible and/or warranted. The saying goes: “if it is worth removing the tumour, it is worth obtaining a histological diagnosis.”
• If only very narrow or unclean margins can be obtained, the following options remain
• Close monitoring of the tumour (for tumour types where removal is possible at relapse). It may seem a strange approach, but it has been reported for some tumours that the remaining cancer cells are killed by the dog’s own immune system and do not recur even if the margins were not clean;
• Perform another surgical intervention with wider margins around the initial surgical incision immediately;
• Treat with adjuvant chemotherapy. This is useful for tumours known to respond to certain chemotherapeutics;
• Treat with adjuvant radiation.