An orangutan at the Jungle Village park in Florida is being treated for non-Hodgkin’s lymphoma by a team of keepers, doctors, and veterinarians. This is a great article (with a little video) that hilights the amazing similarities of humans and primates.
Category Archives: cancer
We’ve talked a lot about cancer in the past few weeks. The many wicked faces of cancer is concern enough for pet owners. Thankfully, cancer isn’t a contagious disease…usually. Dogs can get a venereal tumor that is transmitted through sexual contact. Tasmanian devils are also being wiped out of their natural habitat by a type of cancer that is transmitted easily from one devil to another.
The Tasmanian tumors are aggressive. They grow quickly, and they’re disgustingly nasty. Most of the time, they grow on the face. They get so big that the devils can’t eat enough to stay alive. Metastasis to other organs, including the heart, is also very common.
Back on August 12th, I talked a lot about cancer in veterinary patients. I didn’t cover the way we diagnose cancer, though. The process for diagnosing cancer can be quite confusing, so I’d like to take some time today to shed a little light on how we hunt for answers.
We talked about how a mass/tumor/growth is properly termed Neoplasia. Once a mass is discovered, we have to start testing the mass to find out whether it’s benign or malignant, and whether it has stayed put or has spread to other areas of the body, and how aggressive it appears to be.
Step 1 : Obtaining a Sample
In order to learn anything about a mass, we have to be able to observe the microscopic cells that make up the mass. The objective here is to discover, if possible, the tissue in which the mass started to grow. Depending on how we get a sample to observe, we may be able to accomplish the second two steps as well. We can obtain a sample in three ways.
A. Fine needle aspirate.
A needle attached to a syringe is inserted into the mass. The plunger on the syringe is pulled back to create a vacuum that sucks some cells into the needle. The cells in the needle are then gently sprayed onto a microscope slide. We use a special stain to make the cellular structures visible, then observe the sample under the microscope. This method can be performed on-site at the veterinary hospital. In some cases, a general practitioner will send the slides in for a board-certified pathologist to look at. I prefer to have a pathologist verify my observations in most cases.
B. Incisional Biopsy.
A small piece of the mass is cut out and preserved in a special fluid. We send the piece into a lab, where it is sliced into micro-thin layers. These slices are observed under the microscope. This allows a board-certified pathologist to see not only the cells, but how they are arranged, which gives clues about the structure of the mass. The drawback to this technique is that a patient may need anesthesia in order to obtain this type of sample, and we leave the rest of the mass on the patient. If the pathology report comes back as malignant, the patient will need anesthesia again to take the mass off the body. The advantage to knowing what type of malignancy we’re dealing with is that it can tell us the best way to treat the mass. This includes surgical removal or other treatments such as chemo or radiation.
C. Excisional Biopsy.
In this method, the entire mass is removed at one time. Then, the whole mass (or less commonly, a part of it) is then sent in to the lab’s pathologist. As with the incisional biopsy, the pathologist can observe the type of cells and how they are arranged. The advantage here is that we can try to get the whole mass out (leaving nothing behind on the patient) with one trip under anesthesia. However, if we don’t know the tissue type or we’re unsure about the behavior of the mass, the surgery might not get the whole mass out.
When a pathologist looks at cells to determine if a mass is malignant or benign, there is a set of specific criteria to observe in the cells. If enough of these criteria are seen, a mass is called malignant. The criteria have to do with the size, shape, and contents of the cellular structures.
Step 2 : Grading
Once we have a mass identified, and we know the tissue of origin, we have to go through a process called “Grading.” The mass has come from a specific tissue. Hopefully, we know what type of tissue we started with. Looking at the cells may give us that specific answer. However, the cells in a mass are sometimes very different in appearance than the tissue type they started in. How similar the mass cells look to their tissue of origin is the criteria for grading a mass. Higher grades mean that the cells look less and less like the tissue of origin. This is important to know because it can give us clues about how aggressively a mass will behave. It may help us make treatment decisions and shed light on the longterm prognosis for a patient. In most cases, a higher grade tumor is more difficult to treat successfully and has a worse prognosis.
Step 3 : Staging
Masses that are malignant have the potential to spread to other places in the body. That spread, or metastasis, is a very important thing to find as we determine how to treat a patient. Each stage is defined by how far the mass has spread. Lower stages mean the mass has stayed in its immediate area. Higher stages mean the mass has spread to other parts of the body, such as lymph nodes or other organs.
Step 4 : Treatment Plans
Once we know the grade and stage of a mass/cancer, we can develop an individual treatment plan for a patient. Treatment with surgery, chemo, radiation, and/or a vaccine may be used to treat a cancer patient. The grade and stage provide us useful information about the longterm prognosis for cure vs. remission, and how long remission can be expected to last.
Nothing strikes fear into the heart of clients the way cancer does. Even bringing a distant, slim prospect of cancer tends to halt all other pathways of thought. When we look at the human data, it’s no wonder that we’re so afraid.
As of August 12, 2012, the us has approximately 314,145,701 people. In 2012, about 1.6 million new cancer cases are expected to be diagnosed. While the percentage doesn’t seem to be high at all, the personal experiences of those who have dealt with cancer make the case for just how insidious the disease can be.
Cancer is, at its simplest explanation, an abnormal growth of a cell. The DNA – genetic instructions – inside a cell is altered somehow, causing the cell to do things it shouldn’t do. These cells, or groups of cells, may overproduce or underproduce things they’re supposed to make. They also differ from normal cells by displaying different surface proteins.
When we’re talking about cancer, we do need to be careful about which terms we use, so I’ll try to clarify a little.
Neoplasia: “new growth” This is a general term for abnormal cell division that results in a population of abnormal cells. Neoplasia usually results in a tumor. Tumors are also called masses. Some types of neoplasia don’t form a discrete tumor. Any cell type has the potential to undergo the changes that lead to neoplasia. Tumors can happen -anywhere- in the body.
Benign: A mass that does not show aggressive/destructive behavior, and that is unlikely to spread. These tumors do not cause harm to the person or animal.
Malignant: A mass that shows aggressive/destructive behavior, that may spread, and cause great harm to the person or animal. Malignant essentially means cancerous.
So, to review. Any tumor is a neoplasm, or new growth. Some tumors are not harmful, and are called benign. Some tumors are extremely harmful, and are called malignant or cancerous.
All of this terminology matters because when we’re dealing with a tumor, how we treat it depends greatly upon whether it’s benign or malignant. Benign masses of certain types can be left alone and monitored. Cancerous/malignant masses require some kind of treatment, whether it’s surgical removal, radiation, chemotherapy, or some combination of those things.
So why is cancer such a terrible and deadly disease? First, because neoplastic cells can also trick our immune system into thinking that they are normal cells and shouldn’t be destroyed. Our own defenses fail and allow the neoplastic cells to multiply into a mass. Secondly, because this disease originates in the body, it’s very difficult to kill the neoplasm without also damaging or killing the body. Chemotherapy is a perfect example of this. Chemotherapy drugs are designed to kill neoplastic cells. However, some normal cell types are also damaged. Hair follicle cells, for example, can be harmed, which is why human chemo patients can lose their hair. Radiation treatments can kill neoplastic cells, but it also damages tissue around the target area. When treating cancer, we walk a fine line by poisoning the body just enough to kill the tumor, but not enough to kill the patient.
We know exactly what tumor cells do in the body to evade being destroyed by the immune system. We also know that certain types of cancer will release certain chemical signals into the body that we can detect. Our ability to get images of the body in unique ways (MRI, CT sacn, PET scan, Nuclear Imaging, ultrasound, etc.) has also aided us in diagnosing neoplasms early. We still struggle with this in humans and veterinary patients. There are SO MANY types of neoplasia, in so many areas, that we simply can’t screen everything continuously. Despite our best efforts, neoplasms arise.
The conversation with clients about cancer occurs when we’ve found a mass. Most of the time, a simple examination with the naked eye is not enough to tell whether a mass is malignant or benign. Our hands and eyes are not a microscope, so we have a hard time telling whether a mass is truly dangerous. We need to send in a sample of the neoplastic cells for a pathologist to look at. In many cases, this microscopic examination allows us to state with more confidence that a mass is benign or malignant.
Clients frequently ask if there is a blood test for cancer. There are tests out there, but they currently aren’t sensitive nor specific enough for us to know whether they are helpful or not. It’s difficult to screen before a mass is found. And once it has been, it’s far more beneficial to simply send a piece or needle sample of the mass to the pathologist for examination under the microscope. A quick review of opinions from veterinary oncologists indicated that the few widely-known blood tests for cancer are not yet “ready for prime time.” The technology is good, but it’s just not refined enough for us to make or break a case on the results.
The take-home message here is that neoplasia is, in all of its forms, complex and difficult to manage. It requires a lot of investigation to diagnose. It requires extensive, sometimes dangerous, methods of treatment. Our best defense is to be proactive about having pets examined every 6-12 months, and for owners to examine their pets frequently at home for lumps, bumps, and changes. Needle or biopsy samples need to be taken and reviewed or sent to a pathologist for review. Treatment should be instituted as quickly as possible in order to have better outcomes. Just as some people survive cancer, so do some pets. Their chances are far better when we are vigilant.
Please ask questions in the comments! This is a diverse and complex topic that we could spend days and days on. Let me know what you think, or what you’re curious about. Thanks for reading!