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.