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Cancer & Tumors

  • Ovarian tumors are quite rare in North American pets, mainly due to routine spaying practices. This handout discusses ovarian tumors in dogs and cats. The various forms of ovarian tumors, clinical signs, diagnosis, treatment, and prognosis of this cancer are outlined.

  • Primary pancreatic tumors are rare in dogs and cats. Exocrine tumors include adenomas and adenocarcinomas, and endocrine tumors include insulinomas, gastrinomas, and glucagonomas. Insulinomas are the most common type of pancreatic tumor, followed by adenocarcinomas. Both tumors are more common in dogs than cats. Large breed dogs and Siamese cats may be predisposed. Insulinomas are usually diagnosed with the finding of hypoglycemia with normal to high insulin on bloodwork and concomitant clinical signs. Adenocarcinomas typically go undetected until the clinical signs of metastasis are evident. For both tumors, diagnostic imaging and exploratory surgery with tumor removal (or biopsy) and histopathology are needed for a definitive diagnosis. Insulinomas can be treated with surgery and chemotherapy. Surgery is possible with adenocarcinomas, but as the cancer is more diffuse and has usually metastasized by the time of diagnosis, the prognosis is poorer. Chemotherapy and radiation therapy are ineffective in the treatment of adenocarcinomas. Given the high rate of metastasis with these tumors, staging is recommended prior to surgery.

  • Parathyroid tumors are uncommon in dogs and cats. Benign adenomas occur more often than malignant tumors. Keeshonds appear to have a genetic predisposition to developing parathyroid tumors, but no breed or genetic relationship has been established in cats. Pets may exhibit signs of lethargy, little or no appetite, vomiting, and muscle twitching. Diagnosis is confirmed with PTH testing and ultrasound of the neck region after hypercalcemia is observed on bloodwork. Surgery to remove the affected gland(s) is the typical treatment, but ultrasound-guided ablation may be pursued. Careful monitoring of calcium levels post-surgery is important, as some pets may develop transient hypocalcemia and require calcium supplementation. Prognosis is excellent, and the metastatic rate for these tumors is extremely low.

  • 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.

  • Clinical signs of pituitary tumors depend on whether the tumor is functional or non-functional. Functional tumors can cause Cushing's disease in dogs and can cause acromegaly and insulin-resistant diabetes in cats. Non-functional pituitary tumors can enlarge to cause neurological signs. Diagnosis is based on the history, bloodwork, urinalysis, and sometimes a CT scan or MRI. Medical therapy is often the treatment of choice for functional tumors. Radiation therapy is another option and is usually the primary treatment for non-functional tumors.

  • Plasma cell tumors develop as a result of dysregulated production of plasma cells and are relatively uncommon in dogs and cats. Some plasma cell tumors are benign and the most common locations for these tumors are the head, feet, lips, mouth, and ears. The treatment of choice for benign plasma cell tumors is surgical removal, with little to no recurrence if completely excised. Conversely, multiple myeloma is a very malignant cancer that is usually treated with chemotherapy.

  • Pleural effusion refers to the abnormal accumulation of fluid within the chest cavity. The fluid is not found within the lungs, but instead within the pleural sac, essentially meaning the lungs are floating in a chest that is full of fluid. Several conditions can cause pleural effusion, including chylothorax, heart failure, and tumors in the lungs or chest wall. Immediate treatment often requires oxygen support and the removal of the excess fluid by thoracocentesis, which can also then be tested to diagnose the cause of the pleural effusion. Treatment and prognosis vary depending on the underlying cause of the pleural effusion.

  • The definition of a 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.

  • This handout explains post-vaccination sarcomas (also called injection-site sarcomas) in cats. They are a rare consequence of vaccine injections (and other drugs or materials) that can cause a very aggressive form of cancer at the site of the injection. The incidence of this condition, as well as precautions you and your veterinarian can take, are highlighted.