Diagnosing Cancer – Tricks of the Trade

Presenter – Dr Sophia Tzannes, Internal Medicine Specialist from the Small Animal Specialist Hospital in Australia

Nailing a cancer diagnosis is not always as straight forward as we would like it to be with some of our diagnostic techniques just not being, well, diagnostic. After all, which one of us hasn’t had those cytology results come back as non-diagnostic leading to a very awkward phone call with an owner? Last week’s webinar organised by ‘The Webinar Vet’ discussed ‘the tricks of the trade’ for maximising our chances of making an accurate diagnosis and was led by Dr Sophia Tzannes an internal medicine specialist from the Small Animal Specialist Hospital in Australia.

Cytology is one of the main diagnostic tools available to us when trying to establish if a mass is neoplastic and featured heavily in discussions within this webinar. As a cheap and often effective method it is no wonder that cytology is so regularly used but these samples can sometimes be non-diagnostic, and Dr Tzannes wanted to offer some tips on how to minimise the chances of this happening.

Blood contamination is a common cause of poor quality cytology slides and when performing a fine needle aspirate (FNA) Dr Tzannes advises not to apply any negative pressure in obviously vascular lesions. If blood comes into the hub of the needle then it is important to withdraw straight away to minimize blood contamination. Obtaining enough relevant cells to make a diagnosis can also be another challenge faced by those performing FNA’s and Dr Tzannes advises altering your technique dependent on the type of lesion you have. For example round cell tumours such as lymphoma and mast cell tumours readily exfoliate so negative pressure is not necessary when performing an FNA. However spindle cell tumours have relatively low cellularity and sometimes a significant amount of negative pressure needs to be applied (using a 10-20ml syringe) to aspirate. So if you appear to be struggling to get a good cell sample when checked in-house, it may well be worth applying a larger amount of negative pressure. Interestingly Dr Tzannes stated that often the more malignant the lesion, the easier it will be to aspirate, so a low cellularity can sometimes be good news for your patient.

The quality of the cytology slide should always be checked prior to sending away to the lab in order to avoid those embarrassing follow up phone calls with an owner. Dr Tzannes lists a set of questions you should always ask yourself when looking at these slides which include assessing for the presence of different types of cells, the presence of inflammatory cells and infectious agents which is discussed in much greater detail within the veterinary webinar.  Once satisfied the slide is diagnostic it should be packaged and sent off to the lab but Dr Tzannes stressed never to package these slides alongside a biopsy pot with formalin as its fumes will often cause the quality of the slide to deteriorate.

A number of other diagnostic tools were discussed within this veterinary webinar including biopsies, histopathology and immunohistochemistry. Diagnosing lymphoma also featured heavily and one tip given by Dr Tzannes was to FNA as many nodes as possible in order to get an accurate assessment of the disease as the cell populations within each node can vary significantly. It is also now possible to use flow cytometry to differentiate those hyperplastic changes from neoplastic changes which can be so easily confused. For more ‘tricks of the trade’ and especially for those passionate about oncology this really is the webinar for you.

The Stethoscope (MRCVS)

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