Veterinary CPD webinar – An Introduction to Veterinary Surgical Oncology

This blog post summarises the key takeaways from her session, emphasising clinically relevant signs, diagnostics, and management principles.

As Dr Floryne Buishand explains, success in surgical oncology comes down to answering three critical questions for every case:

1. What is it? (Tumour type)
2. Where is it? (Tumour location and extent)
3. How bad is it? (Tumour grade and stage)

The answers to these questions form the foundation of any effective treatment plan.

1. What Is It? Establishing a Diagnosis

Understanding the tumour type is essential before initiating any treatment. Removing a mass without knowing its nature rarely yields a good outcome and can complicate future therapy.

Diagnostic approaches include:

• Cytology: Quick, minimally invasive, and often available in general practice. Recognising basic cell patterns (round cell, epithelial, mesenchymal) and malignancy criteria is invaluable for first-line assessment.
• Histopathology: Necessary when architectural context is needed or cytology is inconclusive. Biopsy options include:
  • Incisional biopsy (sampling part of the mass)
  • Excisional biopsy (removing the entire mass) appropriate only when small size or location means margins won’t compromise future surgery.
• Presumptive diagnosis: Occasionally appropriate when biopsy won’t alter the treatment plan (e.g., splenic masses requiring splenectomy, isolated lung masses).

Biopsy planning is critical. The biopsy tract must be positioned so it can be removed during definitive surgery, minimising contamination and preserving surgical planes. Poorly placed or excessive biopsies can turn a curable tumour into one that requires more extensive surgery or adjuvant therapy.

2. Where Is It? Tumour Staging

Once you know the tumour type, the next step is determining its extent and whether metastasis has occurred. Tumour staging typically follows the WHO TNM system:

• T — primary tumour size and local invasion
• N — lymph node involvement
• M — distant metastasis

Common staging tools include:

• Thoracic radiographs or CT scans for pulmonary metastasis
• Abdominal ultrasound or CT for abdominal involvement
• Advanced imaging such as PET-CT or scintigraphy for detecting metabolic activity or bone metastases

At the RVC, sentinel lymph node mapping is increasingly used to identify the true draining lymph node(s) rather than relying solely on anatomical assumptions. Using contrast-enhanced CT or intraoperative fluorescent dyes (such as indocyanine green), this technique improves accuracy in detecting micrometastasis while minimising patient morbidity.

3. How Bad Is It? — Tumour Grade and Stage

Tumour grade describes histological aggressiveness (usually graded 1–3), while stage reflects clinical progression and spread. Both inform prognosis and treatment planning.

Grading systems vary between tumour types, for example, soft tissue sarcomas use different criteria from mast cell tumours. It’s important to remember that grading is somewhat subjective and may differ between an incisional biopsy and full excision, as more tissue provides a more complete assessment.

Treatment Planning: Surgery and Beyond

Armed with answers to the three key questions, the veterinary team can outline options to the owner. Treatment may involve:

• Curative surgery (wide or radical excision)
• Palliative surgery (reducing tumour burden or alleviating discomfort)
• Adjuvant therapy (chemotherapy or radiotherapy after surgery)
• Neoadjuvant therapy (before surgery to shrink the tumour)
• No further treatment, where appropriate for patient welfare or owner circumstances

Chemotherapy

• Neoadjuvant chemotherapy may reduce tumour size and guide drug selection based on observed response, though delaying surgery carries risks.
• Intraoperative electrochemotherapy applies electric pulses to enhance local drug uptake but can delay wound healing.
• Adjuvant chemotherapy targets microscopic disease postoperatively, once healing is complete.

Radiotherapy

• Neoadjuvant radiotherapy can downsize tumours but increases the risk of delayed healing.
• Intraoperative radiotherapy delivers focused, high-dose treatment directly to the tumour bed but requires specialist facilities.
• Adjuvant radiotherapy is the most common, addressing residual microscopic disease after excision.

Surgical Principles

The “dose” of surgery is defined by the intended margins: