Glossary of Terminology

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adjuvant chemotherapy – Anticancer drugs used to treat a patient after a malignant tumor has been surgically removed or treated with radiation. Adjuvant chemotherapy is used in an attempt to kill any microscopic tumor cells that might remain in the animal’s body. | ↑ Back to Top

alopecia – Hair loss. Alopecia caused by the treatment of cancer is usually temporary, and the hair can be expected to regrow after the treatment is completed. The hair loss induced by radiation therapy is seen locally, in the area that was irradiated. Certain chemotherapy drugs may produce generalized alopecia, or loss of hair over the entire body; although most humans can expect alopecia from these drugs, only a few breeds of dogs experience alopecia from chemotherapy. Cats often lose their whiskers but only rarely lose body hair. | ↑ Back to Top

anaplastic or anaplasia – A description applied to cells or tissues from a cancer when they no longer resemble, in cell appearance or architecture, the tissue from which they originated. This term is sometimes used synonymously with “poorly-differentiated” or “undifferentiated,” as in a “poorly-differentiated carcinoma” or an “anaplastic carcinoma.” For cells to be “differentiated” implies that they have fulfilled the embryological instructions which should have been programmed into each cell, i.e., liver cells (hepatocytes) should look like they came from the liver, and all liver cells should look similar to each other. If a pathologist looks at a biopsy of a tumor from the liver and cannot even tell that it came from the liver, the tumor is said to be poorly-differentiated or anaplastic. | ↑ Back to Top

anemia – A condition in which the patient has inadequate red blood cells and therefore cannot adequately oxygenate tissues, with resultant fatigue and intolerance of exercise. Anemia may result from loss of blood (hemorrhage) or from the inability of the bone marrow to make red blood cells. | ↑ Back to Top

anorexia – Loss of appetite. Anorexia may be caused by the progressive growth of a tumor, or may sometimes be caused by anticancer treatment–especially by chemotherapy. | ↑ Back to Top

benign – A term used to refer to tumors that are slow growing and do not spread throughout the body. Benign tumors are “well-differentiated,” meaning that the tumor cells differ only slightly in appearance and behavior from their tissue of origin. | ↑ Back to Top

biochemical panel – A battery of tests that are done on blood serum or plasma; these tests are used to evaluate function of such organs as liver and kidney, and to measure proteins and enzymes found in the blood. | ↑ Back to Top

biological therapy – Treatment used to stimulate the patient’s immune system to fight against infection or against cancer. Biological therapy is also known as immunotherapy. | ↑ Back to Top

bone marrow – A spongy tissue contained within the center of most of the bones of the skeleton. In this location, the neutrophils, platelets, and red blood cells are made. Chemotherapy frequently suppresses bone marrow production of these cells for at least a few days. | ↑ Back to Top

brachytherapy – See “implant radiotherapy.” | ↑ Back to Top

cachexia of cancer – The gradual wasting away of a patient with cancer, caused by the growth of the malignant tumor. | ↑ Back to Top

cancer – A general term used to describe one of many types of tumors, most of them malignant. | ↑ Back to Top

carcinogen – Cancer-causing agents that affect the DNA and RNA of cells, leading to uncontrolled growth of these cells and tumor formation. For example, second-hand smoke is now known to be an environmental carcinogen. | ↑ Back to Top

carcinomas – A cancer originating from one of the epithelial or glandular structures in the body. The skin, trachea or bronchi, oral cavity, prostate, bladder, and mammary gland are common sites of carcinomas in the dog and cat. | ↑ Back to Top

chemotherapy – The use of drugs to treat cancer. Most chemotherapy drugs work either by damaging DNA or RNA within the cancer cell or by interfering with the ability of the cell to function, thereby killing it. | ↑ Back to Top

chemotherapy resistance – A tumor’s lack of responsiveness to some or all chemotherapy drugs. Chemotherapy resistance is the result of cancer cells having developed mechanisms to prevent or heal the damage caused by drugs previously administered. Sometimes, resistance to all chemotherapy drugs can be seen in a tumor even when none of these drugs have ever been administered. | ↑ Back to Top

cobalt-60 – A radioactive substance that is used as a source for the emission of gamma rays, which are used in the radiation treatment of cancer. | ↑ Back to Top

complete blood count (CBC) – A laboratory procedure to determine the number of red blood cells, white blood cells, and platelets in a sample of blood. | ↑ Back to Top

CT or CAT (computed axial tomographic) scan – An x-ray imaging procedure that uses a computer to produce a series of detailed pictures of an area of the body. | ↑ Back to Top

cycle – A series of chemotherapy drugs that are given at regular intervals to treat a particular cancer | ↑ Back to Top

cystitis – Inflammation or infection of the wall of the urinary bladder. | ↑ Back to Top

cytopathologist – A medical specialist trained in the diagnosis of cells exfoliated into body fluids or aspirated/scraped from tissues in the body. | ↑ Back to Top

distemper – An extremely contagious viral disease of the dog that can cause fever, lack of appetite, discharges from the eyes and nose, coughing, diarrhea, and eventually neurologic signs such as seizuring. Vaccination is extremely effective in preventing this common disease of dogs. | ↑ Back to Top

electron beam – A stream of electrons (small negatively charged particles found in atoms) that can be used for radiation therapy. Electrons are emitted from a device called a linear accelerator or “linac.” | ↑ Back to Top

endoscopy– A diagnostic procedure in which a fiber-optic tube is inserted into a lumen or cavity of the body to visualize anatomical abnormalities and to take biopsies of tissue. | ↑ Back to Top

epidemiologist – A scientist who studies patterns of disease and other medical conditions in populations of humans or animals. Cancer epidemiologists have been instrumental in discovering that certain cancers are caused by viruses and environmental toxins, and have helped to discover that some cancers have a hereditary basis. | ↑ Back to Top

epithelial – Cells originating from the epithelium, the layer of tissue covering the skin and all the glandular tissue of the body. Epithelial tissue also lines the airways (trachea, bronchi), the mouth, the urinary and genital orifices, and the gastrointestinal tract. | ↑ Back to Top

erythrocytes – See “red blood cells.” | ↑ Back to Top

etiologic – Relating to etiology or causation, as in an etiologic agent. | ↑ Back to Top

etiology – The direct cause of a disease. For example, the etiology of some forms of lymphoma in the cat is the feline leukemia virus. | ↑ Back to Top

excisional biopsy – A surgical procedure that is performed in an attempt to remove the entire tumor and, if possible, surrounding normal tissue. After the excisional biopsy has been performed, it is submitted to a pathologist for diagnosis and to confirm whether any tumor tissue was left behind. | ↑ Back to Top

external-beam radiotherapy – A form of radiation therapy which is performed by placing the patient’s tumor under a beam of gamma rays or electrons for a prescribed period of time. External-beam radiotherapy is usually administered in fractions (12-25 radiation treatments given over 4-5 weeks). Each radiation treatment lasts for only a few minutes, and the patient is not radioactive when the treatment is completed. External-beam radiotherapy is also known as teletherapy. | ↑ Back to Top

frozen section – A biopsy taken from a tissue, usually during the midst of a surgical operation; the biopsy is rapidly frozen, sectioned, and stained so that a pathologist can give an opinion as to the diagnosis while the patient is still under anesthesia and the surgeon waits for the result. This technique is often used in women undergoing a biopsy for a breast mass. If the mass is found to be benign, only the lump itself is taken out. If, however, the mass is determined to be malignant by frozen section evaluation, the breast may be removed entirely (mastectomy). Since conventional histopathology takes days to perform tissue sectioning, staining, and evaluation of the sections, a frozen section biopsy often saves the patient having to have two anesthetic procedures—one to take a biopsy and a second one to actually remove the cancerous mass. | ↑ Back to Top

gamma rays – High-energy rays that are emitted from a radioactive source such as cobalt-60 and that are used for external-beam radiation therapy. | ↑ Back to Top

gastrointestinal tract – The digestive system, which includes the mouth, esophagus, stomach, small intestine, colon, and rectum. Most of the cells lining the gastrointestinal tract divide more rapidly than most of the other types of tissue in the body. Because chemotherapy damages rapidly dividing cells, gastrointestinal side effects like nausea, vomiting, and diarrhea are common. | ↑ Back to Top

hematogenous metastasis – A process by which cancer cells spread throughout the body. Hematogenous metastasis involves tumor cells entering blood vessels and being carried in the blood to distant sites. When the tumor cells reach these organs, they begin to grow and proliferate, forming new tumor masses or nodules. | ↑ Back to Top

hemorrhage – Bleeding. When the term “hemorrhage” is used, the amount of blood loss is usually relatively large. The term “hemorrhagic” as used to describe a fluid or the color of a tissue biopsy, however, usually means red or blood-tinged, and does not necessarily imply severe loss of blood. | ↑ Back to Top

hepatitis – Infection or inflammation of the liver. Canine infectious hepatitis is a viral infection of the dog that can cause liver failure with jaundice and bleeding. Vaccination can protect nearly completely against this infection. | ↑ Back to Top

histopathology – The science or study dealing with the diagnosis of abnormal or diseased tissue. When a histopathologic biopsy is received by a pathology laboratory, the tissue is embedded in paraffin, cut into thin sections that are put onto a slide, and stained. Then, a pathologist makes a diagnosis by evaluating the stained slide under a microscope. | ↑ Back to Top

hormones – Proteins produced by the endocrine glands of the body, such as the thyroid gland and the pancreas. Hormones are released directly into the bloodstream and cause specific effects on cells and organs in distant locations in the body. | ↑ Back to Top

immunotherapy – See “biological therapy.” | ↑ Back to Top

implant – A radioactive material such as gold, strontium, or iridium that is placed into the body to deliver a therapeutic dose of radiation directly to a cancer. | ↑ Back to Top

implant radiotherapy – A form of radiation therapy in which small radioactive beads or needles are implanted into a tumor to deliver a therapeutic dose of radiation. Sometimes, these implants are removed after the appropriate radiation dose has been administered. In other cases, however, the implants lose all their radioactivity after a number of days, and they may be left in the patient’s body without any danger. Implant radiotherapy is also known as brachytherapy. | ↑ Back to Top

incisional biopsy – A surgical procedure that removes a small piece of a tumor for submission to a pathologist. Although excisional biopsies are preferred, in some cases the entire tumor is impossible to remove or its removal would be life-threatening to the patient; in these cases, an incisional biopsy is necessary to make a diagnosis, so that a therapeutic modality other than surgery may be considered. | ↑ Back to Top

induction – A phase at the beginning of treatment with chemotherapy in which higher doses and more types of drugs are used, in an attempt to kill enough tumor cells to bring the patient into remission. | ↑ Back to Top

injection – A procedure (often called a “shot”) to push fluids or drugs into the body, using a syringe and needle. | ↑ Back to Top

intramuscular (IM) – Administered into a muscle. | ↑ Back to Top

intraoperative radiation therapy – A technique which delivers a large dose of external-beam radiotherapy to a tumor during a surgical procedure. This procedure allows surrounding normal tissues to be shielded (protected) from the effects of the radiation. It also allows the radiation therapist to administer a larger dose of radiation to the cancer than might otherwise be possible. | ↑ Back to Top

intravenous (IV) – Administered into a vein. | ↑ Back to Top

irradiate – To treat with radiation therapy. | ↑ Back to Top

laparoscopy – A diagnostic procedure in which a fiber-optic tube is inserted into the abdominal cavity to visualize organs such as liver and spleen. If an abnormality is noted, it is often possible to collect biopsies from the tissue, using a biopsy instrument inserted into a chamber in the laparoscopic tube. | ↑ Back to Top

linear accelerator (linac) – A device used to produce a high-energy, high-speed beam of charged particles like electrons for use in radiation therapy. | ↑ Back to Top

lymphoma – Cancer of the lymph nodes or other lymphoid tissue in the body. Although most lymphomas do originate in the lymph nodes, some may begin in the spleen, liver, bone marrow, skin, or brain. The term “lymphoma” is used interchangeably with “lymphosacoma.” | ↑ Back to Top

lymphosarcoma – See “lymphoma.” | ↑ Back to Top

malignant or malignancy – A term used to describe a cancer that generally grows rapidly and is capable of spreading throughout the body. The term “malignancy” is sometimes used interchangeably with the term cancer. | ↑ Back to Top

mast cell tumor – A common skin tumor in the dog that is also seen occasionally in the cat. These tumor cells have within their cytoplasm granules that stain purple with blood stains and that contain histamine, a substance that sometimes causes the tumor to swell and itch. Mast cell tumors can metastasize to other sites in the body, usually by the lymph nodes and lymph channels. | ↑ Back to Top

manoma or melanosarcomael – A benign or malignant growth of the pigmented cells of the skin and mouth, common in the dog but rare in the cat. The malignant version of this tumor, called a melanosarcoma or malignant melanoma, can spread rapidly both into lymph channels and through the bloodstream. | ↑ Back to Top

medical oncologist – A medical specialist involved with making the diagnosis, staging the tumor, and prescribing a rational course of treatment. Medical oncologists are involved with the administration of chemotherapy; they also often recommend surgery or radiation therapy, procedures that are usually performed by other specialists. | ↑ Back to Top

metastasis – A site of tumor spread, usually within a lymph node or organ distant from the location of the primary or original tumor. Cancers can metastasize by the blood vessels (hematogenous or blood-borne metastasis) or by the lymphatics (the lymph channels that drain lymph, a body fluid, from one lymph node to another). | ↑ Back to Top

metastasize – A malignant tumor’s ability to spread throughout the body, usually through the blood or lymph channels. | ↑ Back to Top

metastatic – Term used to describe cells or a tumor that is capable of metastasizing (spreading). It is also used to describe a mass of tumor in some other location distant from the primary tumor. For example, in describing an x-ray of the chest, a radiologist may say, “The lungs contain several circular metastatic nodules.” | ↑ Back to Top

molecular biology – The science that studies cells using techniques that reveal their molecular makeup, particularly relating to those molecules that concern genes and heredity. | ↑ Back to Top

monoclonal antibody – A protein that is formed by lymphocytes and plasma cells in response to a foreign substance that has entered the body; the adjective monoclonal refers to a protein of uniform size and type that is formed by one single clone or group of these antibody-producing cells. Monoclonal antibodies directed against a specific kind of cancer are sometimes administered as an immunotherapeutic modality to kill cancer cells. | ↑ Back to Top

mutation – A mistake in a cell’s genetic material; at the gene level, a mutation is a change in the DNA of the cell that is passed down from the parent cell to its descendants in subsequent cell divisions. Mutations may be the result of either new genetic material inserted into the DNA or of a deletion of genetic material. They may be caused by agents that damage the DNA, such as toxic chemicals or radiation (x-rays, ultraviolet radiation), or may be just an accident that occurs occasionally when cells reproduce. | ↑ Back to Top

myelosuppression – Lack of production of white blood cells, red blood cells, and platelets in the bone marrow, often caused by damage induced by chemotherapy. | ↑ Back to Top

nadir – The lowest blood cell count caused by chemotherapy treatment. For most chemotherapy drugs, the oncologist can predict approximately when the neutrophil and platelet nadir will occur. | ↑ Back to Top

neoadjuvant chemotherapy – Anticancer drugs used before surgery or radiation therapy, in an attempt to shrink the tumor and make it more amenable to treatment. | ↑ Back to Top

neoplastic – See “neoplasm.” | ↑ Back to Top

neoplasm or neoplasia (plural) – A growth of any new or abnormal cells or tissue in the body; the cells of a neoplasm proliferate autonomously, without the normal mechanisms that control the dividing of non-neoplastic cells. | ↑ Back to Top

neutropenia – A low neutrophil count. If the neutropenia is severe, infection is much more likely. | ↑ Back to Top

neutrophil – White blood cells that are produced in the bone marrow and fight bacterial infection throughout the body. | ↑ Back to Top

occult blood test – A test performed on a sample of the feces. It is used to detect small (usually invisible) amounts of blood being passed by the patient in bowel movements. If the test result is positive, there is concern that there may be a bleeding tumor or ulcer of the gastrointestinal tract, and more diagnostic testing will generally be necessary. | ↑ Back to Top

“-oma” – A suffix used to identify a tumor, usually benign. For example, adenoma is a benign tumor of the glands of the skin. | ↑ Back to Top

oncology – The medical science or specialty concerned with the diagnosis and treatment of neoplasia. | ↑ Back to Top

oncologist – A medical specialist who practices oncology. | ↑ Back to Top

orally – Administered by mouth. | ↑ Back to Top

osteosarcoma – A cancer that originates in the bones, arising from the bone cells themselves. This tumor is commonly seen in the dog, especially in the large or giant breeds. It is most frequently found in the bones of the legs. Osteosarcomas are particularly malignant, spreading rapidly through the body via the bloodstream. | ↑ Back to Top

ovariohysterectomy – A surgical operation to remove the ovaries and uterus of a female animal, commonly referred to as a “spay” procedure. | ↑ Back to Top

palliative – To reduce the severity of symptoms without the intention of cure; this adjective is used to denote a treatment that is intended only to decrease clinical signs associated with the cancer, without any hope that the therapy will lead to a cure. For example, palliative radiation therapy may be used to shrink an enlarged, cancer-filled lymph node in the neck so that the patient’s breathing and swallowing are less difficult. | ↑ Back to Top

papilloma or polyp – Wart-like projections from epithelial surfaces like skin, nasal cavity, or intestine. | ↑ Back to Top

parvovirus – An extremely contagious disease of the dog that causes vomiting, diarrhea, and a severely decreased white blood cell count. Vaccination can protect against this viral disease. | ↑ Back to Top

pathologist – A medical specialist who examines slides prepared from tissue biopsies, in order to make a diagnosis of the disease process that is present in that tissue. | ↑ Back to Top

platelets – Blood cells that are produced in the bone marrow and assist in the formation of a blood clot, thereby helping to stop bleeding. | ↑ Back to Top

primary tumor – The neoplasm at the site at which the first tumor cells began to grow in the patient’s body, i.e., the location at which the “first” tumor originated. In lung cancer, for example, there may be a “primary lung tumor” (usually the largest tumor) and “lung cancer metastases”—smaller nodules of lung cancer that have spread from the first or primary tumor. | ↑ Back to Top

prognosis – An assessment of the likely outcome of a patient’s cancer. A prognosis may be given for no treatment or for various treatment modalities applied to the tumor. It must be remembered that a doctor’s assessment of prognosis is always an educated guess, based on data from current literature, the doctor’s experience with this type of cancer, and the tumor stage. In giving a prognosis, the doctor must also take into consideration such factors as the patient’s age and other medical problems. | ↑ Back to Top

prophylactic – Term used to describe a method used to assist in the prevention of a disease. For example, prophylactic radiation therapy may be given to the lymph channels and lymph node(s) draining a primary tumor site, since microscopic tumor cells may be present in these areas with no clinical evidence. The radiation is given in the hope that it will kill these microscopic cancer cells and thereby increase the chance of a cure. | ↑ Back to Top

protocol – The “recipe” of drugs used to treat a particular tumor, along with the doses and the schedule for administration of each drug. | ↑ Back to Top

radiation – Energy carried by waves or a stream of particles and used to kill cancer cells. | ↑ Back to Top

radiation field – The area of the body that is to be treated with radiation therapy. | ↑ Back to Top

radiation oncologist – A medical specialist who plans, prescribes, and administers radiation therapy for the treatment of cancer. | ↑ Back to Top

radiation therapy – Cancer treatment using high-energy ionizing radiation, either as a beam of gamma rays, electrons, neutrons, or photons, or as a radioactive implant. | ↑ Back to Top

radioactive – Capable of emitting high-energy rays or particles. | ↑ Back to Top

recurrence – The reappearance of cancer cells at the same site or in another location after a disease-free period. | ↑ Back to Top

red blood cells (RBCs) – Cells that are made in the bone marrow and circulate within the blood vessels, supplying oxygen to tissues throughout the body. RBCs are also called erythrocytes. | ↑ Back to Top

remission – The partial or complete disappearance of all signs of cancer, usually as the result of anticancer surgery, radiation therapy, chemotherapy, and/or biological therapy. It is important to realize that remission does not necessarily mean that all tumor cells are gone from the patient’s body, since a few microscopic cells may remain and the cancer may ultimately recur. | ↑ Back to Top

sarcoma – A cancer originating from the non-epithelial tissues of the body, such as the fibrous connective tissue, fat, bone, and cartilage. | ↑ Back to Top

staging – An assessment of the extent of the tumor. The diagnostic procedures for staging are used to evaluate invasion of the tumor into bone or other surrounding tissue, cancer involvement in lymphatics and lymph nodes, and spread of tumor into other organs (hematogenous metastasis). Tumors are usually described as Stage I, Stage II, Stage III, Stage IV, etc., depending on how far the tumor has spread; these stages are different for different kinds of cancer. | ↑ Back to Top

subcutaneous (SQ or Subcu) – Administered under the skin. | ↑ Back to Top

surgical oncologist – A medical specialist who perform specialized surgical operations to remove cancerous growths. | ↑ Back to Top

systemic radiotherapy – A form of radiation therapy in which a radioactive isotope is given orally or by injection. The patient is radioactive for a period of days to weeks after this isotope has been administered and is usually isolated during this time. The length of time the patient is radioactive depends on which isotope was given and on the dose that was administered. A commonly-used form of systemic radiotherapy in veterinary oncology is radioactive iodine treatment of cats with hyperthyroidism, which is caused by a benign or malignant thyroid nodule. | ↑ Back to Top

teletherapy – See “external-beam radiotherapy.” | ↑ Back to Top

thoracoscopy – A diagnostic procedure in which a fiber-optic tube is inserted into the chest cavity to visualize internal organs such as lung. If an abnormality is noted, it is often possible to collect biopsies from the tissue, using a biopsy instrument inserted into a chamber in the fiber-optic tube. | ↑ Back to Top

thrombocyte – See “platelet.” | ↑ Back to Top

thrombocytopenia – A low platelet count. If the thrombocytopenia is severe, hemorrhage may result. | ↑ Back to Top

treatment port or field – The place on the body at which a radiation beam is aimed. | ↑ Back to Top

transmissible venereal tumor (TVT) – A tumor of the dog in which transmission of the cancer from dog to dog occurs from the implantation of tumor cells onto or into tissues. This transmission commonly occurs by breeding—hence the term “venereal” in the tumor’s name. TVTs bleed a great deal, and a bloody discharge from the penis or vagina is a common presenting sign. | ↑ Back to Top

tumor – An abnormal growth of tissue in which cells proliferate more rapidly than in the tissue from which they originated. | ↑ Back to Top

white blood cells (WBCs) – A group of cells that circulate in the blood and fight infection. Some types of WBCs remove bacteria or other infectious agents from the body, while others make antibodies. | ↑ Back to Top

x-rays – High-energy radiation that is used in low doses to create diagnostic images and in high doses to treat cancer. | ↑ Back to Top