My pet has a lump! How can I tell if it is cancerous?

My pet has a lump! How can I tell if it is cancerous?

My pet has a lump! How can I tell if it is cancerous?

The discovery of lumps, bumps, growths and swellings on our pets is a common reason for visiting the vet. Tumours, cysts, insect bites, allergic reactions, skin tags, warts, abscesses and foreign bodies such as grass seeds are just a few of the growths you might find on or under your pet’s skin.

Some lumps are harmless; others are more sinister, but how do we tell the difference?

Unfortunately, it is impossible to determine whether a lump is cancerous simply by looking at or feeling it. It is possible for something that appears superficially harmless to actually be malignant, and for angry-looking growths to be benign (non-cancerous). It is also possible for a pet with 10 harmless lumps (such as lipomas, which are fatty lumps between the skin and the underlying muscle), to have an 11th lump which is not so harmless. Therefore, take note of the exact location of any new growths (so you can find them again) and have them checked by your vet, especially if they are pea-sized or larger, growing rapidly, changing in appearance or annoying your pet.

The only way for your vet to diagnose any lump/growth is by taking a sample and analysing the cells. This might be via a fine needle aspirate (FNA) or a biopsy. With FNA, a needle and syringe are used to collect cells from inside the lump; these are then transferred to a glass slide and examined under a microscope. With biopsy, a small tissue sample is removed from inside the growth for analysis. A growth which appears small on the surface can extend much further than expected under the skin (like an iceberg), so no lump should ever be removed before being identified. Additionally, cancerous and non-cancerous lumps will be approached and handled very differently during surgical removal. 

As a specialist surgical nurse, I’ve seen countless lumps which have needed to be referred to a veterinary oncologist or specialist surgeon because they were not addressed early. If removal is warranted, it should be done while the lump still appears small, minimising the risk of spread of cancerous cells (metastases), and because larger lumps can be more difficult and complicated to remove with “clean margins” (ie: no tumour cells are left behind). Delays in diagnosis and treatment can also result in a longer post-operative recovery time for your pet. It is also advantageous, where possible, to put your pet through a single surgery only, rather than 2+ surgeries if your vet discovers during the first surgery that they cannot remove the entire tumour the first time.

Because cancer can only be diagnosed by analysis of the cells, a “keep an eye on it…let’s wait and see” approach will not give you the answers you need. If a lump turns out to be benign, that’s great, both for you and your pet. If it is diagnosed as cancerous, early diagnosis and treatment is often curative. The longer you wait, the more complicated, stressful, expensive, and less successful the outcome might be.

Even if a lump is diagnosed as non-cancerous, it might still require treatment. The take-home message is if you notice a lump or growth, get it checked and identified sooner rather than later. As your pet’s caretaker and advocate, you have the right to ask for any growths you find on your pet to be tested in order for you to make an informed choice about how to proceed.

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