This involves the vet popping a fine needle into the lump and sucking back on a syringe. The idea is to flake off a few cells and harvest them in the needle hub. These are then puffed out onto a slide and looked at under the microscope.
For some lumps, this gives a quick answer. However, this method does have drawbacks. Some lumps are so tightly knit that the cells don’t flake off and no sample is obtained. Another problem is that an accurate result relies on taking a representative sample of cells. For example, it can be like working out what flavour a cake is just tasting the icing.
But the good news is that many of the common harmless bumps, such as fatty lumps, give their cells away easily which makes a swift diagnosis possible.
If an FNA doesn’t give an answer or the vet’s suspicions are aroused, then a biopsy may be suggested. These take two forms:
Excisional Biopsy: If the lump is small, then it may be simplest to remove the whole thing and send it away for analysis.
A Small Sample Biopsy: But if the lump is large or in a tricky place, then sending a small piece away can tell the vet if drastic surgery is necessary or not.
If the results come back suggesting something sinister, the vet may suggest additional tests such as a chest x-ray, abdominal scan, or FNA from the lymph nodes. This is called ‘staging’ and is used to work out if the cancer has spread, which is important when deciding on treatment options.