Oncology Index

These tumors are polyp-like growths with a narrow base or a stalk. Some are nodular overgrowths secondary to inflammation but others are benign or malignant cancers of the glands found in this area. Most are from the specialized sweat (ceruminous) glands of the ear. These glands produce watery secretion (cerumen) that keeps the ear moist. A few tumors arise from the sebaceous glands that produce an oily secretion and a few originate from the surface epithelium (squamous cell carcinomas). Malignant tumors may spread to other parts of the body.

Most pituitary tumors are benign (and a few are non-cancerous cysts) but because of their location, they still produce serious adverse effects as they enlarge and they are rarely curable. Many produce hormones that have effects on the glands normally targeted by pituitary hormones, and have a knock-on effect on the targets of the hormones of these glands. The most common hormone produced by pituitary tumors stimulates the adrenal cortex leading to clinical signs associated with overstimulation of these glands.

Lymph is a fluid which circulates in the body, transporting cells of the immune system (lymphocytes and macrophages) and draining areas where excess fluid or debris has accumulated, for example in inflammation. Macrophages (literally "big eaters") are cells that "eat" (phagocytose) and digest other cells, infections, and debris. They also collect and carry antigens to the lymphocytes. Macrophages are filtered out of the lymph in swellings called lymph nodes (glands). Within lymph glands there are concentrations of lymphocytes. The ’B’ type lymphocytes, through their derivative ’plasma cells’, make antibodies to the antigens brought by the macrophages (humoral immunity); and the ’T’ type lymphocytes prepare themselves to attack the foreign antigens (cellular immunity).

Mast cells originate in the bone marrow but complete their development in peripheral tissues. They are found in all tissues of the body but are concentrated in the skin, respiratory tract and digestive tract. Mast cells interact with cells of the immune (protective) system producing allergic type antibodies (IgE), presenting foreign molecules (antigens) to immune sytem cells and recruiting certain cells (phagocytes) to engulf foreign or invading material. As well as being a cellular barrier to external agents, mast cells have a regulatory function on cutaneous nerves, blood circulation, fibrous tissue and other immune cells. They are therefore important in allergic responses, tissue remodelling, wound healing and non-allergic skin diseases. Mast cells in hair follicles also help to regulate the cyclical activity of those follicles.

Cutaneous (reactive) histiocytosis is an uncommon condition of dogs. The condition is poorly described in the scientific literature and has various grades all of which may be found in one animal. Other names include "sterile" granuloma/pyogranuloma syndrome. It is a non-cancerous proliferation of mixed reactive cells, predominantly histiocytes but also including white blood cells (neutrophils) and lymphocytes.

Salivary cancers are almost invariably malignant tumors originating from the secretory cells of the glands. Other swellings or tumors of salivary glands may be due to infections and cysts. The glands may also be swollen because of infiltrates of other cancers including those of fat, lymphoid, mast and melanocyte cells.

Tumors of the spleen are common in older dogs. Most enlargement of the spleen is not cancerous and due to blood accumulating as a result of poor circulation, often with bleeding within the spleen (hematomas). Sometimes excessive work in making blood components (hemopoiesis) or excessive breakdown of blood cells cause enlargement. Tissue overgrowths (hyperplasias), either of lymphoid cells or macrophages with fibrous tissue (fibrohistiocytic nodules) are also common. Less commonly, enlargement is due to infection or inflammation of the spleen (splenitis).

Squamous cell carcinoma in situ is a disordered growth of the skin epidermis that may extend to include epithelium of the upper part of the hair follicles. 

This tumor is a disordered and purposeless overgrowth of sweat gland cells. Most sweat glands are attached to the hair follicles (paratrichial) but a few are not associated with follicles (atrichial). Most sweat gland tumors are benign and can be permanently cured by total surgical removal. Malignant tumors that spread to other parts of the body are rare.

The thyroid gland is a two-lobed organ wrapped partially around the front of the trachea (windpipe) just below the throat. Its function is the production and release of the thyroid hormones. Hormones are specialized chemicals that regulate and integrate many activities to maintain internal stability of the body. The hormones, as released, from the various hormone-producing sites (endocrine glands) pass directly into the blood to affect target cells elsewhere. The distinct endocrine glands besides the thyroid are the adrenals, parathyroids, pituitary and islets in the pancreas, although hormones are also produced by many cells in other tissues.

These are tumors arising from structures within the eye. They tend to result in an increase in the internal pressure (glaucoma), which then leads to blindness. There is sometimes bleeding within the eye, swelling and pain.

Bladder tumors vary from pre-cancerous, chronic, hyperplastic inflammation (cystitis) to benign papillomas and malignant carcinomas. ’Transitional carcinoma’ is the most common name given to tumors of the lining of the urinary tract with ’urothelial carcinoma’ sometimes used for those arising outside the bladder (in the urethra). There is gradation and progression from the benign to malignant types so both hyperplasia and metaplasia (change from the normal type of tissue) are regarded as pre-malignant. Animals with malignant tumors do not usually survive longer than a year. Less commonly cancer may arise from the muscle of the bladder. These tumors rarely metastasize.

Most swellings and tumors of the uterus are not cancerous. The most common in the bitch is cystic endometrial hyperplasia (overgrowth of the inner lining of the uterus) due to hormone stimulation. Sometimes, this reaction is deeper in the muscle layers and is called ’adenomyosis’. Secondary infection and inflammation then convert the endometrial hyperplasia into pyometra (literally pus in the womb). Cysts and polyps of the endometrium can also be part of the pyometra syndrome or be due to congenital abnormalities. They may persist when the cause is removed and may be multiple.

These are tumors of the blood vessels. Some are benign (hemangioma) but most are malignant (hemangiosarcoma). The benign tumors usually remain undetected unless they rupture and cause internal bleeding. Provided this is not massive enough to be life-threatening, they can be cured surgically. The malignant tumors spread to other parts of the body (metastasize) and are often not noticed until they are present in many sites. The most common of these sites are the spleen, heart and liver but they may occur anywhere including the mouth, intestine and bones. This group of tumors also includes some rare types such as the epithelioid angiosarcoma, which can occur in the mouth.

The year my pit bull Sam was diagnosed with cancer was a rough one. First he got the diagnosis; then came surgery to remove five tumors from his neck, back, and hind leg. After that, he under went chemotherapy to blast any remaining cancer cells from his system. Those toxic treatments made my normally high-energy dog lethargic and sad.

When my dog Sam underwent his first treatment for cancer at New York City’s prestigious Animal Medical Center, no fewer than five mast cell tumors were removed from his handsome physique. Few would call Sam handsome now, with his Frankenstein-esque, 8-inch-long scars on his neck, back, and hind leg.

What is an adipose tumor?
Almost all tumors of adipose tissue (fat) are slow-growing and benign. They are called lipomas. The tumors are usually permanently cured by full surgical removal. Rarely, they may keep growing and cause problems because of their size and infiltration of adjacent structures. A few tumors (liposarcomas) are well-demarcated but of low grade malignancy so they recur locally. Spread to other parts of the body (metastasis) is extremely rare but there is a syndrome of multiple tumors called lipomatosis.

Endocrine glands produce specialized chemicals called "hormones." These regulate and integrate many activities to maintain internal stability of the body. The hormones pass directly into the blood to affect target cells elsewhere. The distinct endocrine glands are the adrenals, thyroid, parathyroids, pituitary glands and islets in the pancreas although certain hormones are also produced by many cells elsewhere in the body. The pituitary gland at the base of the brain links to other endocrine glands and regulates hormone production by the adrenals, thyroid and sexual organs as well as growth and our day to day cycles of activity (diurnal rhythm).

What is an anal sac gland tumor?
This tumor is a disordered and purposeless overgrowth of cells originating from the modified sweat glands of an anal sac. There are a pair of anal sacs, one each side of the anus between the external and internal anal sphincter. The glands normally produce bad-smelling grey-brown granular secretions. The tumor is usually rapidly growing, almost always malignant (spreading), and extends deep into surrounding tissues. There can be abnormal hormone production by the tumor cells and these hormones can cause widespread physiological effects in the animal. The malignant tumor (anal gland carcinoma) may also spread to other parts of the body (metastasize), but such metastasis is usually slow to occur.

What is a benign mammary tumor?
This is any tumor originating from the mammary gland tissues. Most tumors of this type are cured by total surgical removal but a few progress to malignancy in time and start to spread to other parts of the body (metastasis). A dog may have multiple tumors in different mammary glands.

What are bone and joint tumors?
Non-cancerous bone tumors are rare and mainly due to abnormal development. They include bone cysts and single or multiple lumps of bone in abnormal places (exostoses). Fibrous dysplasia is another developmental condition that causes bone swelling around areas of bone destruction. ’Craniomandibular osteoarthropathy’ of some terriers is a disease of the head bones.

What is the bone marrow?
The bone marrow is the soft tissue inside the bones. Before birth, the marrow contains the primary (stem) cells from which all red and white blood cells will be formed. After birth some types of blood cells, particularly lymphocytes, are made in other parts of the body but the marrow remains the main site for production of circulating blood elements including platelets (which are vital to stop bleeding and make the blood clot), red cells (which carry oxygen) and most white cells (which fight infections and clear up debris).

What is calcinosis?
Calcium deposits in the skin have a variety of causes, usually of minor significance in the young but indicating serious disease in some older animals.

What types of treatment are available?
The standard treatment for almost all cancers is surgical removal of the lump, sometimes with part or all of the affected organ. Other treatments (special types of surgery, radiation treatment or drug treatment (chemotherapy) are not suitable for all cancers. Before selection or advice on these alternative treatments, there must be an accurate diagnosis of the cancer type and its extent in the animal. Cancer treatments often have significant side effects and many are available only at specialist centers, or are still under development for use in animals.

What are connective tissue and nerve tumors?
All tissues and organs of the body may develop cancer (an abnormal overgrowth of their constituent cells). Every organ (liver, lungs, spleen, kidneys and so on) contains a supporting framework of fibrous connective tissue as well as nerves to relay information to and from the brain. Most organs also contain muscle tissue and special cells (histiocytes or macrophages) whose function is to clear debris. Cancers of these tissues can therefore occur anywhere in the body.

Histiocyte biology
Langerhans cells were first recognized under the microscope in 1868 by a medical student, Paul Langerhans. These cells are members of the histiocyte group, which are part of the body’s immune surveillance system. They take up and process foreign antigens, such as pollens and viral, bacterial and fungal microorganisms.

What is this lump?
Cysts are hollow spaces containing liquid or solidified secretion. A few cysts form within cancers but only non-cancerous cysts are considered here.

What is cytology?
Cytology is the microscopic examination of cell samples.

Cancers of the pancreas are of two main types, those arising from the part which produces enzymes to aid digestion (exocrine) and those arising from the groups of cells that produce hormones such as insulin (endocrine). Both groups of tumors may be benign (pancreatic adenomas) or malignant (pancreatic carcinomas).

Muscle (called "smooth muscle") and fibrous connective tissues form the framework (stroma) that holds other tissues together in the organs of the body. They enable these organs to contract and stretch as part of their function, for example in digestion of food. A number of different tumors can develop from the cells of these tissues.

A "tumor" is a lump. Not all are cancerous. Panniculitis is usually visible as a lump but it is an inflammation of the subcutaneous fatty tissue and is not cancerous. Steatitis is a similar inflammation of fatty tissue but occurs in any part of the body.

A "tumor" is a lump. Most, but not all, are cancerous. A large number of different types of tumor, with a bewildering array of names, but often of confusingly similar appearance, can occur in association with the tissues around the eye.

Papillomas are benign, but sometimes multiple, tumors caused by viruses. They are commonly known as "warts". The tumors often disappear spontaneously because the animal slowly develops immunity to them, but some papillomas may need to be removed surgically because they are inflamed, bleeding or infected. They are permanently cured by total surgical removal and do not spread to other parts of the body although there may be multiple tumors.

Parathyroid tumors in dogs include non-cancerous cysts, formed before birth. Enlarged parathyroid glands due to cell overgrowth (hyperplasia) may be secondary to chronic kidney disease and unbalanced nutrition. Most parathyroid cancers are benign (adenomas) and slow growing. Some are malignant (spreading). Both benign and malignant parathyroid cancers produce hormones. The hormones produce signs of overactive parathyroids (" hyperparathyroidism") with clinical signs such as weakening of bones with fractures and lameness. Sometimes there is also loosening and loss of teeth.

Fibrous tissue consists of long fibres of the protein, collagen. These fibers form part of specialized tissues such as bone and cartilage but most are in loose or linear arrangements within low cellularity ground substance. This "connective tissue" is present throughout the body connecting and supporting organs and systems. The basic cell responsible for fiber production is a fibroblast. Overactivity in local areas can produce fibrous tissue masses, mostly slow-growing, non-cancerous and with several names. A few are considered to be benign cancers so are called "fibromas".

This tumor is a disordered and purposeless overgrowth of modified sebaceous glands known as the hepatoid glands. These glands only occur in dogs. They are found in the skin around the anus, prepuce and dorsal tail and occasionally other areas of the skin. The tumor cells resemble liver (hepatic) cells. Most tumors are benign and can be permanently cured by total surgical removal. Many are multiple. Malignant hepatoid gland tumors tend to be locally invasive but very rarely spread to other parts of the body.

Tumors of the intestinal epithelial lining include non-cancerous polyps, benign adenomas and malignant epithelial tumors (adenocarcinomas). The polyps and adenomas may be multiple and cause local obstruction. The malignant tumors cause progressive illness and often spread (metastasize) before clinical diagnosis. Secondary tumors are found in the lymph nodes (glands), on the inside lining of the abdomen (peritoneum) and in the liver and lungs. Survival time with malignant intestinal tumors is often only months, although it is longer if the tumor has not spread before surgery.

Multiple tumors in the liver are not always cancers. The livers of older dogs become nodular although this does not have any clinical effects. Multiple nodules (regenerative nodules) with an accompanying increase in fibrous tissue may be the result of previous liver damage including inflammation of the liver (hepatitis). When the fibrosis affects the whole liver, it is called cirrhosis. At this stage, it is progressive and not curable.

The liver has a massive blood supply so many cancer cells from elsewhere arrive within it and start to grow. In dogs metastatic tumors are three times as common as primary tumors and over 30% of malignant cancer is said to metastasize to the liver. Cancer of the lymph cells of the immune system (lymphosarcoma or lymphoma) is the most common type followed by tumors of the blood vessels (haemangiosarcoma) and then tumors of epithelial tissue, particularly from the pancreas. The liver has multiple functions and a variety of different cells within it so primary cancers may arise from the neuroendocrine cells (carcinoids) and tumors of histiocytic, fibrous and muscle tissue also occur. These are discussed in more detail elsewhere.

What is a tumor of the lymphatics?
This is a tumor of the lymphatic vessels of the skin or subcutaneous tissue.

A malignant mammary tumor is a tumor originating from the mammary gland tissues that has been classified as malignant (invasive and capable of spreading). Although some of these cancers are cured by surgical removal, others recur and some spread to other parts of the body (metastasis). A dog that has a tumor of this type often has or will develop further tumors in other mammary glands.

Mast cells originate in the bone marrow but only mature in peripheral tissues. They are found in all tissues of the body but most are near surfaces in contact with the external environment such as the skin, respiratory and digestive tracts. Mast cells produce many chemicals with differing effects on the body (histamine, proteoglycans, neutral proteases and chemotactic growth factors). These chemicals are present in granules in the cytoplasm of mast cells. They are discharged from the cells in response to various stimuli, and they induce inflammatory reactions. Mast cells also interact with cells of the immune system producing antibodies involved with allergic reactions (immunoglobulin E, IgE), presenting foreign molecules (antigens) and recruiting cells (phagocytes) to engulf foreign material. As well as being a cellular barrier to external agents, they have a regulatory function on nerves, blood circulation, fibrous tissue and other immune cells.

Melanocytes are cells that produce a pigment called melanin. They are found in many parts of the body where there is pigment, particularly skin, hair and eyes.

Melanocytes are cells that produce a pigment called melanin. They are found in many parts of the body where there is pigment, particularly the skin, hair and eyes. In embryonic development, melanocytes are related to cells of the nervous system. Melanogenesis (formation of melanin) is a complex process with genetic, hormonal and ultraviolet (UV) control. A suntan is the result of stimulation of these cells by sunlight (UVA and UVB). Inside the eye melanocytes are found in the iris and choroid layers (see diagram).

What types of nasal tumors are there?
In some cases, chronic inflammation of the nose (rhinitis) leads to proliferation (hyperplasia) and formation of polyps in the nose or throat. These are not cancerous but may need removal. The chronic inflammation is often due to infections with viruses, bacteria and/or fungi and also occurs in animals with a tendency to allergies (atopic animals). Some chronic infections predispose to cancer.

What are neuroendocrine cells?
Neuroendocrine cells interact with the nervous system and produce specialized chemical substances called "neuroendocrine hormones". These hormones affect the rates of specific chemical reactions in other cells locally or in other tissues of the body. Together with the nervous system and other types of hormones they integrate and co-ordinate a wide variety of activities to maintain internal stability of the body. The neuroendocrine hormone producing cells are present in glands such as the adrenal medulla, chemoreceptors (aortic and carotid bodies) and pancreatic islets. They are also scattered throughout the body in a variety of organs including the skin, mouth, esophagus, intestine, liver and lung.

What are neuroendocrine cells and chemoreceptors?
Neuroendocrine cells produce specialized chemical substances called "neuroendocrine hormones". Neuroendocrine hormones interact with the nervous system and other hormones to integrate and co-ordinate a wide variety of activities to maintain internal stability of the body.

What are oral tumors?
An epulis (plural epuli) is the clinical name for a swelling on the gums. Several different tumors share this name, often of different origins including the tooth-socket lining and lining epithelium of the mouth. Most epuli are not cancerous but overgrowths (hyperplasias) as a reaction to trauma. These are fibrous (’fibrous hyperplasia’ or ’fibromatous epulis’). If they are more active, often with bone formation, they are called ’peripheral odontogenic fibroma’ (POF) or ’fibromatous and ossifying epulis’). These originate from the tooth forming tissue. A few of this type are cancerous but benign. Occasionally, these become more malignant and invade locally. Rarely, there is spread to lymph nodes (glands) as fibrosarcomas.

What are fibrosarcomas?
Oral fibrosarcomas are rapidly growing, malignant tumors originating from the fibrous connective tissue of the mouth. The tumors are rarely cured by surgical removal. Recurrence in the mouth and spread to other parts of the body (metastasis) are common.

These are uncommon skin tumors in dogs, but occur mainly in middle aged to older animals with an average age of occurrence of 10 years. The tumors can be difficult to diagnose and have been given several different names so the precise incidence is uncertain.

The prostate gland stores sperm after they have been made in the testicles and produces fluid that contains essential nutrients for the sperm. Cancers of the prostate are rare but usually involve the cells that make the fluid. Although true cancer is rare, non-cancerous overgrowth (hyperplasia) of the gland is common. Both the non-cancerous and cancerous growths have similar clinical signs. There is usually pain in the area and pressure on the back passage (rectum) interfering with passing faeces. Occasionally there is infection or interference with passing urine.

This tumor is a disordered and purposeless overgrowth of sebaceous gland cells. These glands are attached to the hair follicles where their function is to lubricate the hairs and skin. Almost all sebaceous gland tumors are benign and can be permanently cured by total surgical removal. Many are multiple. Malignant tumors, which have the potential to spread to other parts of the body, are extremely rare.

Lymphocytes are key cells in the body’s ability to fight and prevent infection (’immunity’). Lymphocytes are found in tissues throughout the body, in the blood and in particular concentration in lymph nodes (’lymph glands’) and other ’lymphoid tissue’. Lymphocytes are of two main types, called ’T’ lymphocytes and ’B’ lymphocytes. Each plays a different role in immunity.

This is a tumor originating from the connective tissue of, or beneath, the skin. The tumor is diverse in appearance and several different cell lines produce tumors of similar appearance. Some pathologists try to classify this group of tumors by their origin cells but this is not always possible. There are therefore several names that can be used for the tumors of this group including fibrosarcoma, Schwannoma, peripheral nerve sheath tumor, neurofibroma and haemangiopericytoma. Most are slow-growing and few have fibrocyte markers. The tumors often recur locally after surgical removal but spread to other parts of the body (metastasis) is rare.

This is a malignant tumor of skin epidermal cells with varying degrees of differentiation. Tumors of this type occur in people and all domestic species. The tumor is related to basal cell tumors. Most can be cured surgically, the exception being those arising in the nail beds. 

Tumors of the epithelial, glandular stomach lining include non-cancerous polyps and some types of chronic (hyperplastic) gastritis. Malignant epithelial tumors (gastric adenocarcinomas) cause progressive illness. This usually starts only a few weeks before diagnosis but within that time, they have usually spread locally and to distant organs. Many recur following surgery. 

The testicle (testis) contains several different cell types. These include the germ cells, which make sperm, the supporting and nourishing Sertoli cells, and the hormone-producing interstitial (or Leydig) cells.

Any one or more than one of these cell types may become cancerous. The germ cells that make sperm may become cancers known as seminomas, the Sertoli cells become Sertoli cell tumors and the interstitial cells become Leydig or interstitial cell tumors. Most of the tumors are benign. The tumors are usually permanently cured by castration. This needs to be total (i.e. both testicles) as many tumors occur simultaneously in both testicles. Spread to other parts of the body (metastasis) is unusual if the cancer is surgically removed at an early stage.

This is a common tumor, only found in dogs. It has a patchy world-wide distribution including parts of the Caribbean, USA, Southern Europe, Asia and Africa. It is transmitted by physical transplantation. It occurs in both sexes and may appear as multiple subcutaneous nodules on the genitalia, lips and other parts of the body.

Two months ago, at a party hosted by Manhattan’s swanky Spike Gallery, I helped unveil a life-size bronze bust of my dog Sam by the talented sculptor Jennifer Weinik. I was feeling celebratory: After a bout with cancer, Sam had been in remission for almost a year.

In his prize-fight against cancer, my dog Sam is looking like a champ to me.

Sometimes, several people have to travel many miles to help one dog beat a dangerous disease.

My dog Sam’s report has returned from the lab: Six of his tumors were benign, but the seventh was a malignant plasmacytoma. The strategy of the doctors at the Center for Specialized Veterinary Care in Westbury, N.Y., is to remove any and all lumps before they have a chance to mutate into something fatal that could spread to Sam’s vital organs.

I waited a while before trying Neoplasene on my dog Sam. This powerful medicine made of alkaloids from the bloodroot plant is touted as an exciting new hope in the fight against cancer, but it’s also somewhat controversial: some veterinarians flat-out refuse to even consider it.

By now, you’d think my dog Sam would be getting suspicious. For the past two weeks, it’s been raining extra-special treats: hot dogs, pizza, falafel, liverwurst, cheddar cheese, burgers (both the meat and meatless variety).

Of all the compelling reasons to quit smoking, this one should make dog lovers sit up and take notice: there’s ample scientific evidence to suggest secondhand smoke can cause cancer in companion animals.