What is a Biopsy and Why Does My Pet Need One?
A biopsy is when a small sample of a tissue, most often a lump or growth, is taken for analysis to determine what it is. Unfortunately it is impossible to tell what a lump is just by looking at it or feeling it. There are many circumstances when your vet may recommend a biopsy prior to surgery or treatment.
Why can’t the lump just be removed?
For some small lumps this may be appropriate. However for larger lumps, those in locations difficult to remove (for example head and legs) and those showing worrying characteristics such as rapid growth or ulceration, a biopsy before surgery is often more appropriate.
A specialised needle for taking a biopsy
A biopsy helps tell your vet the following:
- If the lump is a cancer
- If it is cancer, whether it is benign or malignant
- How aggressively it will behave
- What type of surgery is required to treat it successfully
- Whether treatments other than surgery are appropriate
- What the long term outlook is (prognosis)
Surgery for some types of cancer requires a margin of apparently normal tissue to be removed with the cancer to ensure all the cancer is taken away. This margin can be up to 2-3 centimetres for certain types of cancer. If this type of surgery is not performed as the first surgery then further surgery has less chance of curing the cancer. Incomplete first surgery can significantly compromise future treatment and sometimes survival with cancer.
The smaller ink ring on this dog’s leg circles the mass. The larger ink ring marks the margin of normal tissue to be removed with the mass.
The long term outlook and chance of a cure (prognosis) is also different for different types of cancer. The type of cancer may change an owners’ willingness to treat their pet and the costs involved. A biopsy allows this to be discussed before considering more major surgery
Even within one type of cancer there may be different levels of aggressiveness often called ‘Grade’. This is further important information that a biopsy will provide, as the treatment required and survival varies significantly with grade.
You can’t judge by appearances! These images show 2 masses on chest walls with very similar appearance. The lump on the left was a benign fatty mass and cured with simple surgery. The lump on the right was an aggressive malignant tumour that required extensive surgery to treat it.
How is a biopsy taken?
Biopsies are either taken through a small surgical incision or using a special needle. The needles take a smaller sample but do not require a surgical incision. They are also useful to obtain samples of masses located deeper in the tissues or in body cavities.
Can there be problems with a biopsy?
Complications of biopsy procedures are uncommon. However as with any surgery, wound problems, significant bleeding and infections can occasionally happen. The most common problem with a biopsy is the failure for the sample to give a definitive answer. In general the larger the sample taken, the more likely we are to achieve a definitive diagnosis. However, we expect biopsies provide the correct and definitive diagnosis in about 95% of cases. This is not because the procedure is poorly performed, but because of the limitation of analysing a small piece of tissue.
The other disadvantage to biopsies is the need for sedation or anaesthesia and the additional costs involved. However the benefits achieved by treating the cancer correctly generally will outweigh these issues and may save money in the long term.