Throughout this Web site, the words TUMOR and CANCER are used interchangeably. Technically, a tumor is just a swelling that may or may not be a cancer. Cancer is a disease of uncontrolled cell growth that can be benign (not invasive and does not spread) or malignant (usually invasive into surrounding tissue and capable of spreading to other areas of the body).
For each tumor type, specific terminology is used to denote the origin of the tumor and whether the tumor is benign or malignant. Tumors can develop from any normal tissue type; therefore there are a considerable number of different tumor types. Below are common tumor types listed by location or tissue type. For information about specific tumor types, see the TUMORS BY NAME section.
To better understand cancer terminology, visit the CANCER DICTIONARY at the Web site of the National Cancer Institute and the National Institute of Health .
ADRENAL
Adrenal gland tumors are rare and vary considerably in terms of type, secondary signs, treatment and outcome. Almost any sign may be associated with adrenal tumors. Two general types of adrenal tumors exist-adrenocortical carcinoma and pheochromocytoma. A variety of blood tests and radiographic studies may be needed to confirm a diagnosis. Treatment is generally with surgery, although some cases may respond to medical management. Surgery can be difficult due to frequent invasion of large blood vessels (vena cava) and kidney. Secondary changes due to hormone production from the tumor may complicate treatment.
ANAL SAC
This tumor occurs most commonly in female dogs and is usually malignant (apocrine gland adenocarcinoma). Some tumors result in increased blood calcium levels. Clinical signs may occur due to the mass in the anal sac under the tail, or as a consequence of an elevation in the calcium levels in the blood (hypercalcemia). The hypercalcemia can result in increased water consumption, increased urination, weight loss and vomiting. Many of these tumors have already spread to lymph nodes in the abdomen before the diagnosis can be made. Treatment includes surgical removal of the anal sac and possibly lymph nodes and radiation therapy. Medical treatment of increased calcium may be needed before or after tumor treatment to decrease injury to the kidneys.
ANUS
Tumors of the anus (not the anal sac) are most common in male dogs. Benign tumors (perianal adenomas) are hormone dependent and occur most commonly in dogs that have not been castrated. Malignant tumors (sebaceous gland adenocarcinomas) are not hormone dependent. Benign tumors are treated with local tumor removal (surgery/cryosurgery) and castration (to prevent new tumor development). Treatment and outcome of malignant tumors vary depending on tumor size and possible spread to lymph nodes but generally include surgery and possibly radiation therapy.
BLADDER
Bladder cancer is more common in dogs than cats. Most tumors are malignant (transitional cell carcinoma) and can spread to lymph nodes, bone and lung. Signs include blood in the urine, straining to urinate or signs secondary to tumor spread. Treatment is generally with surgery, although chemotherapy with or without radiation therapy has been utilized in selected cases. Cures are difficult due to an inability to totally remove the bladder tumor and the high chance of tumor spread beyond the bladder.
BONE
Bone cancer is more common in dogs than cats. Most cases are malignant (usually osteosarcoma), but a wide variation in clinical signs, location and outcome, after treatment, exist. When possible, the affected bone is removed surgically (including leg amputation), although radiation therapy is sometimes used to treat the affected bone. Depending on the degree of malignancy, chemotherapy is often indicated after surgery.
BRAIN
Brain tumors are more common in dogs than cats. A wide variety of tumors and clinical signs may be seen depending on the site and size of the tumor, and include blindness, seizures and changes in personality. Diagnosis usually requires a CT or MRI scan. Treatment varies depending on location and size but may involve surgery and/or radiation therapy. Cats with meningioma (a specific brain tumor) have the best outcomes with appropriate treatment.
ESOPHAGUS
These rare tumors result in vomiting, regurgitation or weight loss. Treatment is difficult unless the tumor is benign and surgically removable.
LYMPH NODES
Tumors can begin in the lymph nodes such as with lymphoma, or tumors may spread to the lymph nodes such as with metastatic cancer. Lymphoma is a tumor of cells called lymphocytes belonging to the immune system. This tumor usually involves many lymph nodes and other organs from the beginning and is highly responsive to chemotherapy.
KIDNEY
Kidney cancer is rare in dogs and cats and may start in the kidney itself, spread to the kidney from another whole-body cancer, or be part of another cancer called lymphoma. Signs are varied but include back pain, blood in the urine, weight loss, fever and abdominal enlargement. Treatment is usually with surgery if the remaining kidney is functioning well. Lymphoma is treated with chemotherapy. Response to treatment varies considerably, from good to poor.
LARGE INTESTINE (See Rectum)
LIVER
Liver cancer is not common in dogs or cats. It can start in the liver, or spread to the liver from another cancer in the body. Clinical signs are often vague and include weight loss, loss of appetite, fatigue and possible jaundice. Solitary tumors (even if very large) may be effectively treated with surgery.
LUNG
Lung cancer is less common in animals compared to humans and affects dogs more frequently than cats. It can start in the lung or spread to the lung (metastasis) from another cancer somewhere else in the body. Treatment usually involves surgical removal of the affected lung.
MAMMARY (Breast)
Cancer in the mammary glands is very common in dogs and cats. It is often hormone dependent from its initial development. Dogs and cats that are spayed early in life (less than one year of age) have almost no risk of developing malignant breast cancer. Approximately 50 percent of breast tumors in dogs are malignant and 90 percent in cats. Treatment is with surgery (mastectomy). The role of chemotherapy and radiation are undefined at this time. More than 50 percent of dogs are cured by surgery, whereas cat tumors are more malignant.
NERVES
Cancer of the nerves, which originate in the brain or spinal cord, are uncommon. It may occur close to the brain or spinal cord, which causes the symptoms, or can occur in nerves away from the brain or spinal cord (see soft tissue sarcomas, peripheral nerve sheath tumors). Treatment is with surgery or occasionally radiation.
ORAL
Cancer of the oral cavity is common in dogs and less common in cats. A very wide range of tumors can occur from very malignant to benign. Signs may include difficulty eating, swelling inside or outside the mouth, halitosis and bloody saliva. A biopsy is critical for accurate diagnosis and treatment planning. Treatment is generally with surgery (possibly including bone removal procedures) and/or radiation. The outcome of treatment is extremely variable depending on tumor type, site, size and species.
OVARY
f the ovary is uncommon in dogs and cats. Clinical signs vary and include a distended abdomen from the tumor or fluid production. Some ovarian cancers produce excess hormones resulting in prolonged or absent heat cycles and hair loss. Treatment is surgical removal of the ovaries, and outcomes are good if the tumor has not spread to other sites within the abdomen.
PITUITARY
Pituitary tumors occur in a specialized part of the bottom of the brain. They may or may not result in increased stimulation of various hormones (especially cortisone from the adrenal glands). Signs (increased water consumption and hair loss, among others) may be from overproduction of hormones or related to pressure on the brain causing blindness, seizures or change in personality. Treatment may involve medical management of symptoms or radiation of the tumor itself (especially if large, and causing clinical signs).
PROSTATE
Prostate cancer is rare in animals (compared to humans) and is much more common in dogs than cats. Most cases are in the advanced stages of disease when first diagnosed. Treatment is often ineffective compared to treatment in humans.
RECTUM
Cancer of the colon or rectum (large intestine) is rare. Common signs can include blood in the bowel movement or straining to have a bowel movement. Tumors may be benign (polyps) or malignant. Treatment generally includes surgical removal, or occasionally with cryosurgery (polyps). Prognosis varies depending on tumor type, specific site and completeness of surgical removal.
SKIN
Skin tumors are the most common tumors in dogs and cats. More than half of skin tumors are benign (especially in dogs), but all skin lumps deserve attention for the possibility of malignancy. Taking a few cells out of these tumors (fine-needle aspiration cytology) can help determine benign from malignant tumors. Management may include observation (only if it is conclusively benign), surgery, cryosurgery or, rarely, radiation or chemotherapy. Outcome ranges dramatically based on tumor type, site, size, species and degree of malignancy.
SMALL INTESTINE
Small intestinal tumors are rare and can result in vomiting, diarrhea or weight loss. Treatment is usually with surgery, although chemotherapy may be used to treat intestinal lymphoma.
SPINAL CORD
Spinal cord tumors are rare. They may start in the spinal cord or the spinal cord may be affected by a tumor starting in tissue adjacent to the spinal cord (e.g., bone, nerve or muscle). Signs are usually associated with pain, lameness or paralysis, and vary with which site in the spinal cord is affected. Treatment varies widely and includes surgery, radiation and, rarely, chemotherapy. Outcome also varies widely depending on tumor type, site and degree of spinal cord injury prior to treatment.
SPLEEN
Cancer of the spleen is more common in dogs than cats. Many noncancer conditions can cause enlargement of the spleen or lumps on the spleen. When the spleen does have cancer, it can originate in the spleen or be part of other whole body diseases. Signs of splenic cancer vary from weight loss, fatigue, enlargement of the abdomen and rapid collapse (from bleeding). Treatment is generally with splenectomy (removal of the spleen) and survival varies widely depending on the type of tumor and whether it has spread elsewhere. Chemotherapy is used for treatment (before or after spleen removal) in certain cases.
STOMACH
Stomach cancer is rare in dogs and cats. Signs vary but may include vomiting (especially if blood is present), weight loss, anemia and lack of appetite. Bowel movements may be dark and tarry in nature. Most stomach tumors are malignant with evidence of spread to lymph nodes or liver, making treatment difficult. Treatment is generally with surgery, especially for benign tumors, although they are rare.
TESTICLES
Cancer of the testicles is common in older dogs and rare in cats. Tumors are often benign but malignant forms do occur, especially in undescended testicles. They may produce hormones with secondary signs such as hair loss, feminization or increased prostate size. Treatment is with castration and the outcome is usually excellent.
UTERUS
Uterine cancer is rare in animals and can be malignant or benign. It is more malignant in cats. Signs may include an abdominal mass or vaginal discharge. Some tumors are dependent on hormones for growth and treatment includes removing the ovaries and the uterus (spay).
VAGINA
Tumors of the vagina are more common in dogs that are not spayed. Signs include vaginal discharge, a physical mass and straining to urinate. Growth may increase during heat cycles. Many of these tumors are benign (leiomyoma or polyp) and respond very well to surgical removal and spaying. A rare tumor (transmissible venereal cell tumor) is spread from dog to dog by sexual contact and can be cured with chemotherapy (vincristine).
For each tumor type, specific terminology is used to denote the origin of the tumor and whether the tumor is benign or malignant. Tumors can develop from any normal tissue type; therefore there are a considerable number of different tumor types. Below are common tumor types listed by location or tissue type. For information about specific tumor types, see the TUMORS BY NAME section.
To better understand cancer terminology, visit the CANCER DICTIONARY at the Web site of the National Cancer Institute and the National Institute of Health .
ADRENAL
Adrenal gland tumors are rare and vary considerably in terms of type, secondary signs, treatment and outcome. Almost any sign may be associated with adrenal tumors. Two general types of adrenal tumors exist-adrenocortical carcinoma and pheochromocytoma. A variety of blood tests and radiographic studies may be needed to confirm a diagnosis. Treatment is generally with surgery, although some cases may respond to medical management. Surgery can be difficult due to frequent invasion of large blood vessels (vena cava) and kidney. Secondary changes due to hormone production from the tumor may complicate treatment.
ANAL SAC
This tumor occurs most commonly in female dogs and is usually malignant (apocrine gland adenocarcinoma). Some tumors result in increased blood calcium levels. Clinical signs may occur due to the mass in the anal sac under the tail, or as a consequence of an elevation in the calcium levels in the blood (hypercalcemia). The hypercalcemia can result in increased water consumption, increased urination, weight loss and vomiting. Many of these tumors have already spread to lymph nodes in the abdomen before the diagnosis can be made. Treatment includes surgical removal of the anal sac and possibly lymph nodes and radiation therapy. Medical treatment of increased calcium may be needed before or after tumor treatment to decrease injury to the kidneys.
ANUS
Tumors of the anus (not the anal sac) are most common in male dogs. Benign tumors (perianal adenomas) are hormone dependent and occur most commonly in dogs that have not been castrated. Malignant tumors (sebaceous gland adenocarcinomas) are not hormone dependent. Benign tumors are treated with local tumor removal (surgery/cryosurgery) and castration (to prevent new tumor development). Treatment and outcome of malignant tumors vary depending on tumor size and possible spread to lymph nodes but generally include surgery and possibly radiation therapy.
BLADDER
Bladder cancer is more common in dogs than cats. Most tumors are malignant (transitional cell carcinoma) and can spread to lymph nodes, bone and lung. Signs include blood in the urine, straining to urinate or signs secondary to tumor spread. Treatment is generally with surgery, although chemotherapy with or without radiation therapy has been utilized in selected cases. Cures are difficult due to an inability to totally remove the bladder tumor and the high chance of tumor spread beyond the bladder.
BONE
Bone cancer is more common in dogs than cats. Most cases are malignant (usually osteosarcoma), but a wide variation in clinical signs, location and outcome, after treatment, exist. When possible, the affected bone is removed surgically (including leg amputation), although radiation therapy is sometimes used to treat the affected bone. Depending on the degree of malignancy, chemotherapy is often indicated after surgery.
BRAIN
Brain tumors are more common in dogs than cats. A wide variety of tumors and clinical signs may be seen depending on the site and size of the tumor, and include blindness, seizures and changes in personality. Diagnosis usually requires a CT or MRI scan. Treatment varies depending on location and size but may involve surgery and/or radiation therapy. Cats with meningioma (a specific brain tumor) have the best outcomes with appropriate treatment.
ESOPHAGUS
These rare tumors result in vomiting, regurgitation or weight loss. Treatment is difficult unless the tumor is benign and surgically removable.
LYMPH NODES
Tumors can begin in the lymph nodes such as with lymphoma, or tumors may spread to the lymph nodes such as with metastatic cancer. Lymphoma is a tumor of cells called lymphocytes belonging to the immune system. This tumor usually involves many lymph nodes and other organs from the beginning and is highly responsive to chemotherapy.
KIDNEY
Kidney cancer is rare in dogs and cats and may start in the kidney itself, spread to the kidney from another whole-body cancer, or be part of another cancer called lymphoma. Signs are varied but include back pain, blood in the urine, weight loss, fever and abdominal enlargement. Treatment is usually with surgery if the remaining kidney is functioning well. Lymphoma is treated with chemotherapy. Response to treatment varies considerably, from good to poor.
LARGE INTESTINE (See Rectum)
LIVER
Liver cancer is not common in dogs or cats. It can start in the liver, or spread to the liver from another cancer in the body. Clinical signs are often vague and include weight loss, loss of appetite, fatigue and possible jaundice. Solitary tumors (even if very large) may be effectively treated with surgery.
LUNG
Lung cancer is less common in animals compared to humans and affects dogs more frequently than cats. It can start in the lung or spread to the lung (metastasis) from another cancer somewhere else in the body. Treatment usually involves surgical removal of the affected lung.
MAMMARY (Breast)
Cancer in the mammary glands is very common in dogs and cats. It is often hormone dependent from its initial development. Dogs and cats that are spayed early in life (less than one year of age) have almost no risk of developing malignant breast cancer. Approximately 50 percent of breast tumors in dogs are malignant and 90 percent in cats. Treatment is with surgery (mastectomy). The role of chemotherapy and radiation are undefined at this time. More than 50 percent of dogs are cured by surgery, whereas cat tumors are more malignant.
NERVES
Cancer of the nerves, which originate in the brain or spinal cord, are uncommon. It may occur close to the brain or spinal cord, which causes the symptoms, or can occur in nerves away from the brain or spinal cord (see soft tissue sarcomas, peripheral nerve sheath tumors). Treatment is with surgery or occasionally radiation.
ORAL
Cancer of the oral cavity is common in dogs and less common in cats. A very wide range of tumors can occur from very malignant to benign. Signs may include difficulty eating, swelling inside or outside the mouth, halitosis and bloody saliva. A biopsy is critical for accurate diagnosis and treatment planning. Treatment is generally with surgery (possibly including bone removal procedures) and/or radiation. The outcome of treatment is extremely variable depending on tumor type, site, size and species.
OVARY
f the ovary is uncommon in dogs and cats. Clinical signs vary and include a distended abdomen from the tumor or fluid production. Some ovarian cancers produce excess hormones resulting in prolonged or absent heat cycles and hair loss. Treatment is surgical removal of the ovaries, and outcomes are good if the tumor has not spread to other sites within the abdomen.
PITUITARY
Pituitary tumors occur in a specialized part of the bottom of the brain. They may or may not result in increased stimulation of various hormones (especially cortisone from the adrenal glands). Signs (increased water consumption and hair loss, among others) may be from overproduction of hormones or related to pressure on the brain causing blindness, seizures or change in personality. Treatment may involve medical management of symptoms or radiation of the tumor itself (especially if large, and causing clinical signs).
PROSTATE
Prostate cancer is rare in animals (compared to humans) and is much more common in dogs than cats. Most cases are in the advanced stages of disease when first diagnosed. Treatment is often ineffective compared to treatment in humans.
RECTUM
Cancer of the colon or rectum (large intestine) is rare. Common signs can include blood in the bowel movement or straining to have a bowel movement. Tumors may be benign (polyps) or malignant. Treatment generally includes surgical removal, or occasionally with cryosurgery (polyps). Prognosis varies depending on tumor type, specific site and completeness of surgical removal.
SKIN
Skin tumors are the most common tumors in dogs and cats. More than half of skin tumors are benign (especially in dogs), but all skin lumps deserve attention for the possibility of malignancy. Taking a few cells out of these tumors (fine-needle aspiration cytology) can help determine benign from malignant tumors. Management may include observation (only if it is conclusively benign), surgery, cryosurgery or, rarely, radiation or chemotherapy. Outcome ranges dramatically based on tumor type, site, size, species and degree of malignancy.
SMALL INTESTINE
Small intestinal tumors are rare and can result in vomiting, diarrhea or weight loss. Treatment is usually with surgery, although chemotherapy may be used to treat intestinal lymphoma.
SPINAL CORD
Spinal cord tumors are rare. They may start in the spinal cord or the spinal cord may be affected by a tumor starting in tissue adjacent to the spinal cord (e.g., bone, nerve or muscle). Signs are usually associated with pain, lameness or paralysis, and vary with which site in the spinal cord is affected. Treatment varies widely and includes surgery, radiation and, rarely, chemotherapy. Outcome also varies widely depending on tumor type, site and degree of spinal cord injury prior to treatment.
SPLEEN
Cancer of the spleen is more common in dogs than cats. Many noncancer conditions can cause enlargement of the spleen or lumps on the spleen. When the spleen does have cancer, it can originate in the spleen or be part of other whole body diseases. Signs of splenic cancer vary from weight loss, fatigue, enlargement of the abdomen and rapid collapse (from bleeding). Treatment is generally with splenectomy (removal of the spleen) and survival varies widely depending on the type of tumor and whether it has spread elsewhere. Chemotherapy is used for treatment (before or after spleen removal) in certain cases.
STOMACH
Stomach cancer is rare in dogs and cats. Signs vary but may include vomiting (especially if blood is present), weight loss, anemia and lack of appetite. Bowel movements may be dark and tarry in nature. Most stomach tumors are malignant with evidence of spread to lymph nodes or liver, making treatment difficult. Treatment is generally with surgery, especially for benign tumors, although they are rare.
TESTICLES
Cancer of the testicles is common in older dogs and rare in cats. Tumors are often benign but malignant forms do occur, especially in undescended testicles. They may produce hormones with secondary signs such as hair loss, feminization or increased prostate size. Treatment is with castration and the outcome is usually excellent.
UTERUS
Uterine cancer is rare in animals and can be malignant or benign. It is more malignant in cats. Signs may include an abdominal mass or vaginal discharge. Some tumors are dependent on hormones for growth and treatment includes removing the ovaries and the uterus (spay).
VAGINA
Tumors of the vagina are more common in dogs that are not spayed. Signs include vaginal discharge, a physical mass and straining to urinate. Growth may increase during heat cycles. Many of these tumors are benign (leiomyoma or polyp) and respond very well to surgical removal and spaying. A rare tumor (transmissible venereal cell tumor) is spread from dog to dog by sexual contact and can be cured with chemotherapy (vincristine).
