Discovering that your pet has a lump, and that the ‘lump’ may be quite serious can be a great shock. The nature of investigation and potential surgery can seem daunting and the terminology may seem terribly confusing on top of the initial shock.
I sincerely hope that this goes some way to explaining some of the issues.
What is cancer ?
Cancer is when an abnormal cell continues to grow and replicate. It has no turn off switch and does not respond like ordinary cells to messages which would normally cause cell death.
The lump itself ...
We may refer to it as a mass, or a cancerous growth, or a number of descriptions, including tumour.
A benign mass or tumour is one in which an abnormal population of cells grow but do not spread elsewhere in the body. Nevertheless, in some locations, the mass can still pose problems by it’s effects on the functioning of nearby normal tissues.
A malignant mass or tumour is one in which the abnormal cells not only grow but they have the potential to spread elsewhere in the body, such as the liver, lungs, kidneys, and so their spread harms tissues far away from their original site. This spread is known as metastasis. The picture on the right shows a cell entering the blood stream.
Identifying the mass.
If we know what the tissue actually is, we can better advise you about the best course of action. We can do this by sampling the tissue and getting the opinion of a trained pathologist.
Fine needle aspirate.
This technique involves sucking some cells out of the lump through a needle. A pathologist can then comment on the cells gathered and provide an opinion on their nature.
Sometimes the cells gathered will not reflect the lump itself, and sometimes the quality of the cells will not allow for reliable interpretation but it is a simple technique that is quite easy to perform without sedation or anaesthesia.
This means surgically removing a small piece of the tumour and it provides more information about the cells, their architecture, and their potential to invade surrounding tissues. The arrows show how the different tissues can be identified, and the borders between normal and abnormal.
It does however mean that the patient will undergo one procedure to get a biopsy, and then one to deal with the cancer definitively.
The effects of the tumour.
Blood samples can reveal organ dysfunction elsewhere so giving an idea on the suitability of a patient for an anaesthetic, and for surgery, as well as the possible secondary effects of the tumour, that is the effect of the tumour on other parts of the body. An example may be an elevation in calcium in the bloodstream resulting from hormones released from cancer cells. The calcium may then damage the kidneys.
X-rays and ultrasound.
If a mass is known to be malignant or potentially malignant, x-rays of the chest, and possibly the abdomen can reveal spread. The round white circles are lumps of cancer tissue in the lungs.
X-rays of the chest require two or more views. Unfortunately, they are not perfect because a 1cm lump contains some 9 million cells and a lump needs to be 1/2 to 1cm in size before we can see it on an x-ray.
Ultrasound is particularly useful to examine the liver, and the kidneys where we can see changes in texture and architecture.
In some cases, the nature of imaging may stretch to MRI scanning (right) which is very sensitive and can help to show the position of a lump in greater detail than x-rays can show.
None of these forms of investigation may be perfect because it unfortunately only takes 1 tiny cell to escape our attentions for treatment to effectively fail in achieving a cure.
We operate differently according to the nature of the lump itself. For instance a LIPOMA, a tumour made up of fat cells, is generally benign, and by removing this lump almost by peeling it out, we will achieve a cure.
Some small tumours such as a Mast Cell Tumour can be incredibly aggressive and require relatively wide ‘Margins’.
MARGINS are areas of normal tissue around a tumour that are free of cancerous cells. Imagine Cancer the crab. It has a central body and then claws which spread well away from the body. The ‘claws’ of the cancer can extend into the apparently unaffected ‘normal’ tissue. Failure to remove them may mean that surgery fails and the tumour returns.
For some tumours, achieving a margin may require removal of all the local tissue. This may mean amputating a limb, or removing a tow, or an ear. Some surgery may necessitate removal of large areas of skin and replacing the deficit with skin from elsewhere, know as skin grafting.
This word is very emotive in humans because we associate it with generally looking and feeling dreadful. Humans have a choice to ensure this in order to live. Our animals do not have this choice, we make it for them. That said, the doses of chemotherapy that humans are given do not actually improve the chances of our pets. Some solid form, that is, ‘lump’ forms of cancer can benefit from chemotherapy although we more commonly use it for treating some of the cancers of the blood - the leukaemias, along with a form called lymphoma. lymphoma is a type of cancer affecting the glands in the body that respond to infections. This type of cancer produces solid masses but surgical removal is of little benefit other than to help us confirm diagnosis. It is generally so widespread that chemotherapy forms our main means of treatment. Chemotherapy will often mean a combination of drugs, some given into the veins by injection, and some given orally.
Although relatively common in humans, this is not so commonly used for animals because of the scarcity of units for treating animals. There are not that many units in the country but they are increasing, and are becoming more accessible. Liverpool has a superb oncology unit.
As veterinary surgeons, we know the choices you may face are difficult and we will do our best to provide as much information and the best advice we can.
Above all, we will always have to value quality of life above life itself
and do our best to give the best advice we can.