PetCancerVet

Tel 01423-866594
Fax 01423-869290
e-mail PetCancerVet

61 Wetherby Road
Knaresborough
N Yorks
HG5 8LH

DIAGNOSTICS METHODS IN CANCER

Examination.

Visual examination of a lump, along with careful palpation, can yield clues as to it's nature. A full examination of the patient for other lumps and/or complications which may be associated with certain tumours is a first step in the diagnostic process.

Go to top of page

--------------------

Fine needle biopsy and cytology.

Insertion of a fine needle into the lump can allow cells to be removed and placed on a slide for examination. Whilst some tumours cannot be diagnosed by this method even when examined by expert cytologists, a significant number can be identified, and sometimes their degree of malignancy can be assessed. A simple and quick stain may give a definite diagnosis in some tumours. The slides can be sent to expert cytologists if appropriate.

Lipomas (benign fat tumours) and mastocytomas can be diagnosed easily (usually) by FNAB. None cancerous lumps such as dermal cysts can be differentiated.

The pictures below show stained cells taken from tumours by this method and giving vital diagnostic information about the case.

Go to top of page

--------------------

Solid biopsy and histopathology.

The definitive diagnosis of a tumour is carried out on a solid piece of tissue removed under anaesthetic, either before an attempt is made to remove the tumour, or at definitive surgery. This is sent to a laboratory for histopathological examination.

There are times when a biopsy is needed before an operation to remove the tumour can be planned, though it may often be more practical to remove the whole of the apparent tumour and send it all away for examination. Occasionally the results may suggest that surgery has not been adequate, because the tumour is more aggressive than was thought or because the edges of the tissue removed contain tumour cells.

Any tissue sent for examination must be representative of the tumour: occasionally it is not possible to tell by eye which part to select.

Go to top of page

--------------------

Special tissue stains.

There are many special stains which can be used to give extra information about the identity of cells and their behaviour. Most involve highly specialised techniques and can only be done at specialist laboratories, but there is one which is relatively simple.

It is called AgNOR staining and shows up bits left over in cell nuclei after division. Normal cells should be tidy and have one or perhaps two AgNORs, but fast dividing tumour cells have more. There is evidence to suggest that the number of AgNORs per nucleus is related to the degree of malignancy in certain tumours, whilst their significance in others is less sure. This picture shows the AgNORs in the cells from the tumour above left:



Go to top of page

--------------------

X-ray.

X-rays are, of course, one of the main ways to look inside a body to obtain information about disease. Experience allows a radiologist, which all vets have to be, to see not just bone, but soft tissue organs. Many pets with cancers will have their chests X-rayed to check for the presence of secondary (metastatic) tumours in the lungs. It is important to remember that a lump smaller than about 1cm is not necessarily visible on a chest X-ray and that the cells or clumps of cells that spread to the chest are microscopic, so an X-ray can only detect well establish metastases.

With special techniques using radio-opaque dyes it is possible to gain extra information. The X-ray below shows a tumour in a neck bone of a dog and a dye injected around the spinal cord shows the tumour is squashing the cord:



Go to top of page

--------------------

Ultrasonography.

Most people know about ultrasound scans for pregnancy. The imaging technique has many more uses. It allows us to see inside organs such as the liver to search for metastases as well as primary tumours which would not be detected by X-ray. Also, fluid filled organs such as the bladder will show very clear pictures on ultrasound scan. The picture below shows a cancer in a dog's bladder. This was removed surgically and the dog was given 6 months of chemotherapy (during which she was well and lively) and she is still alive 5 years later:



Go to top of page

--------------------

M.R.I.

This is the latest type of scanning and is available for pets in 2 centres in the UK. It is an expensive technique but the images obtained are immensely detailed. MRI scans can be very useful in planning treatment of tumours but we usually have to manage without them on grounds of cost.

Go to top of page

--------------------

Exploratory surgery.

There are times when none of the above methods will give enough information and we have to resort to surgical exploration to assess a tumour. Generally this will be combined with an attempt to remove the tumour, or at least to obtain biopsy specimens.

Go to top of page

--------------------

Staging.

Staging is the assessment of local, regional and distant spread of the tumour, and of complicating factors if any. Proper staging can give a good idea of the chance of success of surgery of other modality of treatment. It is the sum result of all the investigations described above.

Go to top of page