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Educational Articles

Cancer & Tumors

  • Many herding breeds (most commonly Collies and Australian Shepherds) have a mutation at the MDR1 gene that makes them more sensitive to the negative effects of certain medications. These drugs include several antiparasitic agents (when given at high doses), the antidiarrheal agent loperamide (Imodium®), and several anticancer drugs. The effects of the mutation vary in severity, depending on whether the dog carries one or two copies of the mutation. There is a cheek swab or a commercially-available test that assesses blood samples for the presence of the MDR1 mutation.

  • Rarely, ovarian tissue can be left behind when a dog is spayed. This leads to the ongoing secretion of hormones such as estrogen and progesterone that can result in a dog continuing to have a heat cycle. Ovarian remnants are difficult to diagnose, but vaginal cytology combined with hormone testing can be used to confirm the presence of functional ovarian tissue. Surgical treatment is typically recommended to prevent other health conditions from developing.

  • Pituitary macroadenomas are large tumors of the pituitary gland that are either functional (secrete hormones) or non-functional (do not secrete hormones). The clinical signs depend on the type of macroadenoma, though become severe over time in either case. Diagnosis requires specialized CT or MRI imaging. This handout explains the effects of macroadenomas in cats and the treatment options available.

  • Pituitary macroadenomas are large tumors of the pituitary gland that are either functional (secrete hormones) or non-functional (do not secrete hormones). The most common functional pituitary macroadenoma in the dog secretes the hormone ACTH, causing increased cortisol levels and Cushing’s disease. Non-functional macroadenomas cause clinical signs through compression of nearby structures resulting in vision changes, diabetes insipidus, and neurologic disorders. This handout explains the effects of these tumors on dogs, how they are diagnosed, and the treatment options available.

  • Pneumothorax is an accumulation of air outside the lungs, but inside the chest wall. The air outside the lung prevents the lungs from inflating normally, and can lead to lung collapse. There are several variations of pneumothorax.

  • The American Animal Hospital Association and American Veterinary Medical Association have established guidelines to standardize preventive health care for dogs, helping them to live longer, healthier lives. This handout provides an overview of the recommendations within these guidelines and why they are so important.

  • Radiation is a type of energy produced naturally by the sun, earth, and rocks and artificially by machines. Although several types of tumors can be treated with radiation therapy alone (e.g., nasal tumors, brain tumors, and certain types of lymphoma), radiation therapy is most commonly used to destroy or limit the growth of cancer cells left behind (i.e., microscopic disease) after a tumor has been surgically removed. Side effects depend on the type and location of the tumor and its surrounding tissues.

  • Round cell tumors are among the most common skin tumors in dogs, and they typically form just under the skin, although they may change the surface of the skin above them. It is impossible to diagnose any of them without a veterinary pathologist analyzing a tissue sample of the tumor under a microscope. If detected early, most round cell tumors can be easily removed.

  • Seizures and syncope are commonly confused with one another due to similarities in the appearance of these episodes. Both present with collapse but there are several details, explained in this handout, that can differentiate between them, which is important for determining treatment. The prognosis for each condition varies depending on the underlying causes.

  • Skin gland, hair follicle, and sebaceous gland tumors are often benign. Matrical carcinoma and sebaceous gland adenocarcinoma are rare and more aggressive forms of the disease. Regardless of the type (sweat, hair, or sebaceous) diagnosis is made by fine needle aspiration, biopsy, and/or surgical removal and histopathology. Further treatment is reviewed.