When it comes to cancer surgery in pets, few things linger longer in a vet’s mind than a local tumour recurrence that could have been avoided. Incomplete surgical margins don't just compromise outcomes—they lead to repeat surgeries, emotional stress for owners, and professional frustration.

This article outlines the essential principles of surgical oncology to help ensure your first surgery is your best shot—because in cancer treatment, wide margins can mean the difference between cure and recurrence.

The Importance of a Realistic, Integrated Approach to Cancer in Pets

Cancer in dogs and cats can be overwhelming—but it isn’t always terminal. An optimistic yet realistic mindset is critical. Collaborating with pet owners to establish treatment goals, while balancing tumour biology with available therapies (surgical, medical, and radiation oncology), leads to the best outcomes.

While multimodal treatment is often required, surgery remains the cornerstone for diagnosing and definitively treating solid tumours.

1. Pre-Operative Assessment: Look Beyond Chronological Age, start with a comprehensive evaluation of the pet’s:

• Overall health and signalment

• Concurrent diseases or conditions

Chronologic age alone is a poor predictor of surgical resilience. Physiological status matters most. Stabilising comorbidities—even if unrelated to the tumour—can significantly reduce perioperative risk.

2. Rigorous Cancer Staging: Go Beyond the Surface

Accurate staging is non-negotiable. It informs:

• Prognosis

• Treatment strategy

• Owner communication

Use the WHO TNM system to assess local, regional, and distant disease. A baseline diagnostic workup should include:

• Diagnostic biopsy

• 3-view thoracic radiographs 

• Fine-needle aspirates (FNA) of regional lymph nodes

Note: Palpation is not sufficient. Depending on tumour type, add abdominal ultrasound or 

CT imaging for full characterisation.

 

3. Biopsy: Do It Right the First Time

A properly planned biopsy provides critical insights into:

• Tumour type and grade

• Biological behaviour

Key biopsy principles:

• Choose tools that avoid cell damage

• Orient the incision so the tract can be excised en bloc with the tumour

• Ensure margins remain uncompromised 

Skipping biopsy planning risks misdiagnosis—and compromises definitive treatment.

 

4. Pathology Submission: More Than Just Sending a Sample

Fix tissues in 10% buffered formalin (minimum 1:10 tissue-to-formalin ratio). Always provide detailed clinical history to the pathologist.

On receiving results:

• Review tumour type, grade, and margin status carefully

• Don’t hesitate to query anomalies, request re-sectioning, or seek a second opinion

 

5. Define the Surgical Goal: Diagnosis vs. Cure

Each oncology case must have a clearly defined objective - typically diagnosis, cure, or both. For localised tumours, first surgery offers the best chance of cure.

 

6. Surgical Dose: Err on the Side of Aggression

Select your approach - marginal, wide, or radical - based on:

• Tumour behaviour

• Prognosis

• Comorbidities

• Client expectations

• Adjunct therapies

Common mistake: Under-dosing. 
For malignant masses, a controlled open wound is preferable to leaving tumour cells behind.

Rule of thumb: 
Wide margins of 2–3 cm in all directions, plus fascial planes for depth, are standard for tumours prone to local recurrence.

 

7. Patient and Site Prep: Think Ahead

Prepare the site with wide clipping to allow for extended margins. Address any paraneoplastic syndromes pre-op. If adjuvant therapy (e.g., radiation or reconstruction) is likely, integrate that plan early.

 

8. Intra-Op Technique: Handle with Care

During surgery:

• Treat the tumour like an infectious agent—minimise manipulation

• Ligate blood vessels early

• Lavage the site thoroughly

• Use India ink to mark margins and aid histopathology orientation

 

9. Specimen Handling & Post-Op Planning

Fix and label the entire excised mass with:

• Marked margins

• Accurate slicing and inking

• Clear communication with the pathologist

Pathology results guide next steps. For incomplete margins or high-grade features, consider:

• Repeat surgery

• Radiation therapy 

• Chemotherapy

Ultimately, the goal remains constant: Improve the pet’s quality of life.

 

Learn More: Charles' Surgical Oncology Lecture

For an in-depth discussion, access Charles’ recorded lecture on surgical oncology and wide-margin principles.: Watch the lecture  or listen to the podcast: Wide Margins Save Lives 

Need Support With a Cancer Case?

We’re here to help with any surgical or emergency oncology cases.

📧 aec.moorabbin@aecvet.com.au 
📞 03 9532 5261