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Diagnostic Tests For Cancer

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Types of Cancer
10 Common Signs of Cancer
Common Cancer Terms
Diagnostic Tests
Cancer The Deadly Menace

Though there are many different types of cancer, there are five basic categories:

Carcinomas – the most common cancers, which are those that originate in the tissues which cover a surface or line internal organs. Carcinomas include lung, breast, prostate, skin, and intestinal cancers.

Sarcomas – cancers which originate in the connective and muscle tissue, attacking bones, muscles, cartilage, or the lymph system. These are considered to be the rarest and also the most deadly types of cancer.

Myelomas – these tumors are also rare and originate in the plasma cells, which are found in bone marrow.

Lymphoma – these are cancers of the lymph system.

Leukemias – this type of cancer originates in the tissues of the bone marrow, spleen, and the lymph nodes. Leukemia manifests itself as an overproduction of white blood cells and is not a cancer that forms solid tumors.

Ten Common Signs of Cancer in Small Animals

Abnormal swellings that persist or continue to grow
Sores that do not heal
Weight loss
Loss of appetitie
Bleeding or discharge from any body opening
Offensive odor
Difficulty eating or swallowing
Hesitation to exercise or loss of stamina
Persistent lameness or stiffness
Difficulty breathing, urinating, or defecating

Common Cancer Terms

Cancer:  any malignant, cellular tumor; cancers are divided into two broad categories of
carcinoma and sarcomas.

Neoplasm: an abnormal new growth of tissue in animals or plants; a tumor

Tumor:  1.)  a swelling; a cardinal sign of inflammation.  2.)  neoplasm: a new growth of
tissue in which cell multiplication is uncontrolled and progressive.

Benign tumor:  one lacking the properties of invasion and metastasis and showing a lesser
degree of abnormal cellularity than do malignant tumors.  These are usually surrounded by a
fibrous capsule.

Malignant tumor:  has the properties of invasion and metastasis and displays cells with
widely varying characteristics

Carcinoma:  a malignant growth made up of epithelial cells tending to infiltrate surrounding
tissues and gives rise to metastases.

Sarcoma:  a malignant tumor originating from connective tissue or blood or lymphatic tissues.

Metastasis:  Spread of a tumor from its original location to a remote one, by tumor cells that are carried in the blood.

Growth:  can refer to any kind of an abnormal increase in size of tissue

Lump:  can be a growth or fluid filled cyst or any structure raising above the normal surface of
a tissue plane

 Diagnostic tests for Cancer

Blood tests
Blood tests are a very useful diagnostic tool.  Blood is made up of several different kinds of cells and other compounds, including various salts and certain proteins. Blood contains two main elements: the fluid that is called plasma and cells. There are three kinds of cells: red blood cells, white blood cells and platelets.  Some types of cancer cause direct changes in the blood which can suggest or confirm a diagnosis, such as conditions involving the bone marrow ( leukaemia - cancer of white blood cells). Blood tests are also important to detect secondary infections and anaemia which may require extra treatment and to check the functioning of important body systems in older patients. During treatment, repeated blood samples may be required to check that treatment itself is not causing problems.
 
Cytology
This is the examination of cells using a microscope to identify their nature. The cells are aspirated from the affected area (eg a swollen lymph gland) using a fine needle, a procedure which is almost painless and is usually performed with the patient conscious.The cytology test generally takes 20 to 30 minutes to perform if done in the veterinarian's office. If the sample is submitted to a laboratory, results may not be available for 2 to 3 days.As with all tests, a cytologic examination is neither 100 percent sensitive nor specific. Should a cytology exam be negative or inconclusive, your veterinarian may recommend a full tissue biopsy sample be obtained and submitted for analysis. Negative results can exclude the presence of certain diseases. For example, a skin tumor might be malignant or benign.

Biopsy -A biopsy is the surgical removal of a piece of tissue from your animal  and is necessary in cases where cytology has failed to give a diagnosis or if the lump is hard and cannot be penetrated by a fine needle. Biopsies may be performed surgically, or using special biopsy devices. The procedure is normally carried out under local or general anaesthesia. Again, the sample is examined microscopically. If the tissue is cancerous, the biopsy provides important information regarding the type and nature of the cancer.In most cases a report will be available in three working days. However, in some instances this may take longer. These include: bone biopsies which need to be softened prior to processing, special staining techniques that may be required to identify cells, cell products, bacteria, fungi, etc, difficult or unusual cases for which the pathologist will seek a consultation with other pathologists.

Endoscopy
This is a means of looking directly inside a body cavity using a long, narrow rigid or flexible telescope called an endoscope without invasive exploratory surgery. The major disadvantage with endoscopy is the need to anesthetize the patient which necessitates pre-anesthetic evaluations such as blood tests, radiographs (xrays), and/or ultrasound to see whether the patient will withstand anaesthesia.  Animals are fasted for 12 hours before an endoscopy is performed. In cases where the lower intestinal tract is to be examined, the patient should be fasted for 24-48 hours.  Pets are generally required to be admitted for the day (2 days for colonoscopy). Sedation or anesthesia is used to eliminate any pain and to keep the animal from moving. Cancerous masses can be seen and biopsied using special pincer like attachments, avoiding the need for open surgery. Areas of the body commonly examined in this way include the throat and windpipe, the stomach, the large bowel, the bladder and the nose. Endoscopies are usually considered among the low-risk procedures in veterinary medicine.

Gastroscopy

  Gastroscopy allows the internist to closely examine an animal's esophagus, stomach, and the first portion of the small intestine. The health of these tissues can be assessed, biopsies harvested, and sometimes foreign objects can be retrieved. The pet is fasted at least 12 hours prior to the procedure, and is often released in the same day. Common reasons this technique is employed are weight loss, vomiting, diarrhea, and anorexia.  

Bronchoscopy

Bronchoscopy is fiberoptic examination of the respiratory system. This includes the larynx (voice box), trachea (windpipe), and bronchial tree. This is a short, day procedure that allows the internist to take samples and bacterial cultures of the airways. It may be preceded by chest radiographs (xrays), and certain blood tests. Animals requiring this test usually are sent because of a chronic cough, suspected pneumonia, allergy, or cancer.

Colonoscopy

 Colonoscopy allows the doctor to evaluate disease processes of the large intestine (colon), and rectum. Patients requiring this technique are usually admitted to the hospital the day prior to the scheduled procedure, to allow for medical evacuation of the bowel. This facilitates a visual exam of the tissues and harvesting of a biopsy. This process is recommended for animals that have chronic diarrhea, straining to defecate, and/or blood in their stools.

Rhinoscopy

Rhinoscopy is the use of fiberoptics to investigate the nasal cavity. It can be used for dogs over 20 lbs., and is a short day procedure. It is usually accompanied by skull and nasal radiographs, and biopsy. Chronic sneezing, snorting, "reverse sneezing," chronic nasal discharge, or nasal bleeding would be indications for rhinoscopy.

Diagnostic imaging - this covers methods of obtaining pictures of the inside of the body, using X-rays, ultrasound, radioactive materials and CT or MRI scanning.

Radiography - is usually the first technique which is used, and can be performed in most veterinary practices. X-ray pictures (radiographs) show the internal structures of the body and will show some deformities of organs that cannot be felt. Bone cancers in particular can often be detected at a very early stage since their radiographic appearance is often quite characteristic and easy to differentiate from benign processes such as arthritis. Radiography is also very useful for looking at the lungs, since they contain air, which appears black on the radiographs, and outlines solid structures clearly. However soft tissues such as muscle and liver appear a uniform grey even when they contain abnormal areas. Radiography is used to delineate a known abnormality or to check other parts of the body, usually the lungs, for secondary tumours which may have spread from the first lesion. Radiography can also be used to monitor the progression or reduction of a known cancer over period of time.

Ultrasound -
An ultrasound scan is a painless test that uses sound waves to create images of organs and structures inside your body. It is a very commonly used test and as it uses sound waves and not radiation, it is thought to be harmless and most people are familiar with its use in examining human babies before birth. It can be used for pregnancy diagnosis (as soon as 21 days after the last breeding date).   Ultrasound allows diagnostic tests to be performed with the aid of safe, sound waves. The waves bounce off the animal’s internal organs (or a mass), and are decoded into an image on the monitor. This is a powerful and versatile technique in which a skilled ultrasonographer can see, measure, and assess the health of many internal organs. In many cases, it can preclude the need for major surgery. The way the ultrasound bounces back from different tissues can help to determine the size, shape and consistency of organs, structures and abnormalities. So, it can help to monitor the growth of an unborn child, and check for abnormalities, detect abnormalities of heart structures such as the heart valves. (An ultrasound scan of the heart is called an echocardiogram,) help to diagnose problems of the liver, gallbladder (such as gallstones), pancreas, thyroid gland, lymph nodes, ovaries, testes, kidneys, bladder and breast. For example, it can help to determine if an abnormal lump in one of these organs is a solid tumour or fluid-filled cyst, detect abnormal widening of blood vessels (aneurysms).

If a tumor is suspected, its presence can be proven, its tissue biopsied, and a fairly accurate assessment can be made as to whether or not the tumor is operable. This assists the veterinary surgeon in planning and preparing for the surgery. This is a rewarding technique to evaluate the liver, spleen, adrenal glands, pancreas, kidneys, prostate, bladder, and uterus. It is not, however, the primary tool used in disease of the stomach or intestines.

It can differentiate between different types of tissues and also between fluid and solid matter. Its importance in cancer diagnosis lies in its ability to detect small abnormalities deep within organs and to allow precise, 'ultrasound guided' aspirate or biopsy to be performed. A good example would be aspiration of cells from small nodes in the spleen to differentiate between benign reactive nodules and cancers; without ultrasound guidance there would be a good chance of aspirating normal splenic cells.

The ultrasound examination itself, is virtually risk free in most cases. It can usually be done without anesthesia or sedation, and requires about 30-40 minutes. If a biopsy is required, sedation and/or anesthesia (brief) may be required. A review of your pet’s medical records, tests, and a physical examination would generally proceed the ultrasound. For these reasons, patients are fasted at least 12 hours prior to the appointments (which are generally scheduled in the morning). For your pet’s safety, and procedure planning, it is best to assume your animal will be admitted to our hospital for a least a few hours. Biopsies are usually done with small needles, thus avoiding surgery. The tissues are sent by courier to board certified pathologists. The turnaround time is about 4-7 business days.

Echocardiography

Echocardiography is specialized ultrasound of the heart. The heart’s action and functions can be studied in detail. Several sets of measurements can be made which aid in the determination of type and severity of an animal’s heart dysfunction. This information gives veterinarians aid in prescribing medications that can alleviate signs and symptoms of heart disease. It can also be used as a monitoring technique. Generally, no anesthesia is required, but a brief stay at the hospital can be expected (1-2 hours usually). Additional information (a data base) may consist of chest x-rays, an electrocardiogram, and analysis of any fluid present in the chest cavity. Patients are often referred because of known or suspected heart disease, fluid around the heart or in the chest, evaluation of heart murmurs, or suspected chest or heart tumors.

Scintigraphy
 Scintigraphy is a diagnostic technique which uses a sophisticated camera to obtain two-dimensional images showing cancer and other tissue abnormalities which are too small to be seen with other techniques.  Using advanced computer technology, these images can then be analysed to provide both qualitative and quantitative information. If, for instance, illness or injury is causing increased metabolic activity or blood flow, the area involved will emit a higher level of gamma radiation (seen on the image as a 'hot spot').

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Cancer: The Deadly Menace

First printed in Double Helix Network News, Winter 2002

by C.A. Sharp

We waited in our vets exam room for Sydneys x-rays to be developed. He had an abnormal bony lump on his right foreleg, just below the shoulder.

Sydney was a rescue who had been saved from a county pound only to bounce through several homes before finding his forever home with us. And now we were facing the possibility that this happy, affectionate little blue merle Australian Shepherd had osteosarcoma, a deadly bone cancer.

Cancer is one of those frightening words you never want to hear in connection with someone you love, human or animal. Cancer can be disfiguring. It can cause terrible suffering; even the treatments available are often harrowing. Cancer can kill.

Anyone who has had to face cancer inevitably asks, Why?� People wonder what they did wrong to bring this terrible situation upon their loved ones. The truth is that most aspects of cancer development are beyond our control, though there are some things dog owners and breeders can do to reduce the risk, as we will discuss later.

Cancer isnt one disease, but a whole class of diseases in which cells proliferate abnormally and at the expense of the host. Cancer cells multiply at abnormal speed, invade other tissues and are incapable of performing their normal functions. There are several sub-classes of cancers. Carcinomas are cancers of the epithelial tissues, the skin and internal linings of the body; sarcomas affect connective tissue, bones, muscles, cartilage and even blood vessels; leukemias occur in the white blood cells; and lymphomas in the lymph system.

Cancer is seen most frequently in elderly dogs, half of whom will be affected. It occurs more often in purebreds than mixes and some types of cancer are more frequent in certain breeds. Cancer is the most common non-accidental cause of death for dogs.

Common canine cancers include breast cancer, sarcomas, lymphoma and squamous cell carcinoma, a skin cancer. Mast cell tumors, another type of skin cancer, are the most common. Interestingly, dogs rarely suffer some cancers common to humans, including lung, colon and ovarian cancer, probably due to dogs� differing physiology and life-style. The canine reproductive system is different in both form and some aspects of function. Dogs have much shorter digestive tracts and different dietary needs and habits, and they don�t live as long. And dogs don�t smoke, though they do live with smokers and exposure to second-hand smoke can be even more dangerous.

Some breeds have particular cancer problems: Large and giant breeds are more prone to osteosarcoma, Bernese Mountain Dogs to hystosarcoma, and black Standard Poodles to squamous cell carcinoma, to name a few.

Cancers are genetic in origin, though they are not likely to be inherited. However, all cancers are caused by genetic mutations. Most of these do not occur in germ-line, or reproductive, cells. Cancerous mutations are not confined to alterations made to genes. Chromosomes can be damaged as well. Sometimes, for reasons yet unknown, a chromosome will tangle, a condition called knotty DNA. If this happens near a tumor suppressor gene, cancer may result. Transpositions, where bits of one chromosome switch places with bits of another, can also lead to cancer. Chronic myelogenous leukemia in humans is an example: A bit of chromosome 22 attaches itself to chromosome 9 forming a Philadelphia Chromosome (named for the place of its discovery.) In so doing, it fuses two genes together, leading to proliferation of leukemia cells.

More frequently, cancers are caused by copying errors or direct DNA damage caused by things like chemicals or ultraviolet light. It is normal for a dogs cells to divide, making copies of the chromosomes in the process. This happens many thousands of times from conception to death. No copying system is perfect; the DNA code is subject to occasional misprints, scrambled content and deletions. Over time, mistakes will accumulate. Cancer is more frequent in the elderly because they have undergone far more cell divisions and had longer exposure to environmental conditions that can cause this kind of damage to the DNA.

But not all cancers occur in the old. Exposure to radiation or toxic chemicals can cause DNA damage leading to cancer. Some individuals are born with mutations that predispose them to cancer. Wilms� Tumor is an inherited kidney cancer that occurs in children. Cancers have been linked to viruses, which hijack a cells DNA machinery to reproduce themselves. During this process, cells can wind up with viral DNA inserted into their own. Depending on which genes are affected by the insertion, cancer may develop.

The cell is not without methods of counteracting these mistakes. There are redundancies in the system designed to render some mutations unimportant, if not eliminate them altogether. For example, there are housekeeping genes that form proteins designed to repair or snip out and discard damaged sections of DNA. If sufficient DNA damage has occurred, tumor suppressor genes, such as BRCA1 and p53, induce apoptosis, causing the defective cell to self-destruct. Not surprisingly, many cancers have been linked to mutations in tumor suppressor genes. BRCA1 mutations are very common in human breast cancer. Many cancers in humans and dogs are associated with p53 mutations, including canine mammary cancer. If a mutation occurs in a germline (reproductive) cell, that mutation will be inherited. However, both copies of the tumor suppressor gene must be damaged before it loses its ability to protect the cell.

Proto-oncogenes are a type of gene which regulates normal cell growth and division and thereby prevent cells from multiplying wildly. When these genes mutate, they are called oncogenes. Oncogenes can render tumor suppressor genes inactive. They can be dominant or recessive, so a mutation in a single copy may lead to cancer.

Another example, of redundancy designed to prevent serious DNA mistakes is written into the DNA code. Within every gene are triplets of base pairs called codons. They are like words in the code. They produce bits of RNA necessary to cell function. The bases, adenine, guanine, cytosine and thymine, commonly noted as A, C, G, and T, will only form A-C and G-T pairs. When making RNA, the double-stranded DNA unzips and collects complementary bases (though RNA substitutes a uricil for thymine.) The DNA code TAC will form the complementary RNA codon GCA, which ultimately results in a particular particular amino acid being used in at a particular point in a protein. However the DNA codons TAA, TAG and TAT will result in the same amino acid being used. If a copying error occurred that changed TAA to TAT, there would be no effect on cell function.

A dog owner or breeder has only a small amount of control over environmental factors that can lead to cancer. The fact that these diseases are a major cause of death among humans shows that we are a long way from being able to control all the risks. But taking the same kind of precautions with your dogs that you do for yourself and your family will help. Provide clean water, minimize exposure to polluted air and, for dogs with unpigmented or lightly-pigmented skin, avoid excess exposure to bright sunlight. Limit unnecessary exposure to chemicals like pesticides. Avoid overuse of beneficial chemicals like medications, parasite controls, and even common home and garden products. A good, balanced diet is important. Research on canine dietary links to cancer has been limited, but the numerous studies citing connections positive and negative of certain items or food preparation processes in human cancers indicates this is likely the case with dogs as well. Whether you use a commercially prepared feed or a homemade diet, make sure it contains proper levels of the anti-oxidant vitamins like C and E, and substances like elegiac acid, which studies have show can improve function of the tumor suppressor p53. This wont guarantee that all of your dogs will be cancer free, but it will help.

Some aspects of cancer control are more directly in a breeders hands. Because certain breeds of dog and certain families within a breed will have a tendency to develop certain cancers, the breeder should learn which cancers are most likely to occur and note which dogs have had them. With this knowledge and careful mate selection, the breeder can reduce the risk of producing dogs that will develop those cancers. For example, if a dog and bitch each had a grandparent that had osteosarcoma, it would be unwise to breed them to each other Do not breed for traits that may pre-dispose a dog toward cancer, like large areas of unpigmented skin. .

Another factor that can contribute to cancer is inbreeding. Purebreds are more cancer-prone than mixes and some breeds have particular cancers more frequently than dogs in general. All breeds are of necessity to some degree inbred; each represents only a segment of the over-all canine gene pool, including both desirable and undesirable genes. Within breeds, there is evidence that dogs with higher coefficients of inbreeding (COI) are more likely to develop cancer at a younger age than those less-inbred individuals within the same breed. It is definitely true that if a cancer-causing mutation is present in germ cells in an individual, inbreeding or linebreeding on that individual will increase risk of producing offspring that inherit two copies of that mutated gene. In view of this, breeders would do well to avoid increasing COI and, where possible, make mating selections that will lower it.

On a broader level, it would be extremely useful if breed clubs and breed health organizations would conduct cancer surveys to discover exactly what kinds of cancer are occurring within a breed and at what ages. This knowledge will not only let breeders know what to watch out for but indicate areas of research which the club or group might want to target for funding.

The fifteen minute wait for Sydneys x-rays seemed to last forever. Finally, our vet came in and snapped the films onto the viewer. I had the good news before he could tell me. Sydney did not have cancer. At some time in his past, his leg had been broken, possibly due to being kicked, and he had been left to heal on its own. The bone had mended well but was misshaped. No tumor, no cause for worry this sad episode from Sydneys past was long behind him. With heartfelt thanks to our vet, we left his office knowing that our gentle young dog would be with us for many happy, healthy years to come.

reprinted with kind regards from C.A. Sharp
Pres. Australian Shepherd Health & Genetics Institute, Inc.
http://www.ashgi.org Editor, Double Helix Network News

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The above information is simply informational. It's intent is not to replace the advice of a veterinarian nor to assist you in making a diagnosis of your pet. Please consult with your own veterinarian for confirmation of any diagnosis. Your pets life may depend on it.