The Dog Cancer Survival Guide (32 page)

A biopsy is a surgery, typically a small one, which removes tumor tissue for examination by a pathologist. It is more definitive than a fine needle aspirate, and can show the type of cancer and its grade (how aggressive it is). All biopsies are done under anesthesia or heavy sedation with pain control, so that the dog cannot feel the surgery.

Most biopsies are incisional, which means they don’t remove the entire tumor and some tumor cells are knowingly left in the body. There are several tools that can be used, depending upon the nature and the location of the tumor. These include a scalpel, which takes a wedge shaped sample, or a core punch, which takes a disk shaped sample. Occasionally, an excisional biopsy is done, which is when the entire visible tumor is removed (with a scalpel).

Biopsy reports are extremely useful because they give the diagnosis and a detailed description of the cancer cells. They will also often report the tumor type, grade and sometimes a margin evaluation (which tells you if the entire tumor was likely removed). The lab may also include comments about the cancer’s likely prognosis – but these comments, unfortunately, could be viewed as facts. Keep in mind that the biopsy report is only one part of the story, and your dog’s prognosis is not based solely on this one item.

For a more complete and reliable prognosis for your dog, it’s best to have a discussion with an oncologist who has examined him, reviewed his medical history, and staged his cancer for spread. Putting that information together with the biopsy report creates a more complete picture.

If a tumor is deep in the body (for example, in the liver), a wide needle might be used to do the biopsy. If an even deeper biopsy is needed – for example, a bone sample – a very long core biopsy needle is used. Imaging tools, like ultrasound, are often used to help guide the needle during fine needle aspirates or biopsies of sites deep in the body.

Internal organs can also be biopsied using an endoscope: a small tube is threaded into the organ, and then a tiny machine with a fiber-optic camera is sent through the tube. The machine also has little arms that can grab and cut tissue samples, which are then pulled back through the tube.

Many clients think vets can “get it all out in the biopsy.” It’s important to remember that biopsies are not usually curative surgeries for aggressive cancers, and almost never “treat” the cancer.

The point of a biopsy is to discern the type of tumor and to figure out how aggressive it is. The type and grade of the tumor determines the treatment plan.

Sometimes an entire lump, the visible part, anyway, is removed during a biopsy. This is usually because the tumor is discrete and easy to remove. It may look to us like the tumor is “gone” after the biopsy – but if the cancer is aggressive, there may be invisible and microscopic cancer cells still left in the region.

Occasionally a vet may biopsy a lump as if it is a curative surgery (often under pressure from guardians who try to squeeze two surgeries into one). She will remove the visible lump, plus a wide margin of tissue, hoping that even invisible cells are removed. The problem with this approach is that if the biopsy report finds the tumor benign, your dog has undergone a bigger surgery for nothing, and if it is a malignancy, your dog may still need another surgery or other treatment.

Careful planning usually saves money in the end, so if you hope to save money by reducing the number of surgeries, and insist upon attempting a curative surgery with a biopsy, I strongly suggest a fine needle aspirate first. Often, an aspirate will help your vet identify what type of cancer is present so that the surgery can be more effectively planned.

It is best to think of a biopsy as a test that is accomplished with a surgery. Just like a blood test does nothing to treat cancer, a biopsy usually doesn’t, either. It’s frustrating, but better to wait until after we get the biopsy report to plan a curative surgery.

Once the biopsy specimen is removed, it is sent to a pathology lab in a preservative, where it is prepared and embedded in a clear plastic. The specimen is sliced very thin, stained, and then examined under a high-powered microscope. The pathologist looks for several things, including the cancer type and grade. Knowing this can help us decide whether and where to look for cancer spread. It can also help us to plan how wide and deep an incision to make during a curative surgery.

Because of all of the steps involved, it usually takes five to ten days to receive your biopsy report after the actual surgery is performed. As you may have already experienced, it feels like ten years.

Despite the expense, the anesthesia, the recovery time, and the stress associated with a biopsy, it is a good idea to get one. Without it, you and your team are in the dark about the true nature of your dog’s specific cancer case, or whether your dog even has cancer. Without a biopsy, it is hard to tailor a treatment plan.

In addition to their usefulness as an initial diagnostic tool, biopsies are done after curative surgeries, also. In these cases, the removed tumor will be sent to the pathology lab and examined along the margins, or edges, to see if there are cancer cells present. This is called a comprehensive margin evaluation. This type of examination can help a vet to know if another surgery or another treatment is in order, because, although some tumors seem very distinct from the surrounding tissue, they may have microscopic cancer cells spreading out in a halo. If the pathologist doesn’t find any microscopic tumor cells, he pronounces the margins “clean” or “complete.”

Clean margins in a sample may mean that the cancer is cured or unlikely to recur. If the pathologist finds cancer cells on the border of the removed tissue, he pronounces them “dirty” or “incomplete,” because it is very likely that cancer cells are left in the dog, too. In these cases, your vet or oncologist may suggest another surgery or some other treatment to target the remaining cancer cells.

Owners whose dogs have had a recurrence (regrowth) of a tumor in the same location often ask me how this could have happened, when the margins were pronounced clean after the first surgery. When I review the pathology reports in these cases, I often notice that while the tumor had “clean” margins, those margins were also very narrow, often only one millimeter. In these cases, the tumor cells were probably in tissue beyond that margin. Those cells, which were left in the dog, caused the recurrence.