"Thymoma" GULF COAST VETERINARY ONCOLOGY'S TUMOR TIDBITS Volume 2, Number 5: April 2001 This Month's Feature: Thymoma DON'T FORGET TO VISIT OUR WEB SITE: CARING FOR PETS WITH CANCER, a comprehensive web site for veterinarians and pet owners caring for pets with cancer. Drug handouts, tumor handouts, case examples, pet loss information, and much more at: Editor: Kevin A. Hahn, DVM, PhD, Diplomate American College of Veterinary Internal Medicine (Specialty of Oncology) & Overall Nice Guy; Gulf Coast Veterinary Oncologists, Houston, TX 77027, drhahn@gulfcoastvetspec.com _____________________________________________________________________ ANNOUNCEMENTS Seeking - Full-time technician (RVT preferred) in Medical Oncology. Available immediately. Monday-Friday, No Weekend or Overnight Duties. Good pay/health and retirement benefits. Seeking - Full-time Medical Oncology Fellow (1 year renewable appointment) and Medical Oncology Resident (3 year nonrenewable appointment). Available immediately. Schedule an appointment with Dr. Hahn or call 713-693-1166 or fax resume to 713-693-1167. ______________________________________________________________________ Tidbit Topic: THYMOMA OVERVIEW: Originates from thymic epithelium and is infiltrated with mature lymphocytes, Rare in dogs and cats, Occurs most commonly in medium- and large-breed dogs, Dogs--mean age, 9 years, Cats--mean age, 10 years. SIGNS: Coughing, Tachypnea, Dyspnea, Swelling of the head, neck, or front limbs (ie, anterior caval syndrome), Muscle weakness and megaesophagus caused by myasthenia gravis. About 20-40% of animals with thymoma are also diagnosed with nonthymic tumors, polymyositis, and other autoimmune diseases. DIFFERENTIAL DIAGNOSIS: Lymphoma, Branchial cyst, Ectopic thyroid carcinoma, Chemodectoma. DIAGNOSTIC FINDINGS: Lymphocytosis in a few patients, Thoracic radiographs reveal a cranial mediastinal mass, pleural effusion, and megaesophagus in some patients, Cytologic examination shows mature lymphocytes and epithelial cells, Evaluate for myasthenia gravis if the patient has signs of muscle weakness, dysphagia, or regurgitation. LOCAL TREATMENT OPTIONS: Surgical excision the treatment of choice. Thymoma tends to be highly invasive and difficult to resect in dogs, but less invasive and easier to remove in cats. Use an intercostal approach for small masses and a sternotomy for large masses. Radiotherapy of potential benefit by reducing the lymphoid component of the mass. CHEMOTHERAPY AND OTHER MEDICATIONS: Prednisone (20 mg/m2 q48h) and cyclophosphamide (50-100 mg/m2 q48h) have been used in a very limited number of patients. Two patients had a partial remission. Vincristine has been used in a limited number of cats and dogs with partial remission (5 pets) and complete remission (1 dog) observed. Myasthenia gravis treated with prednisone and anticholinesterase drugs until the tumor can be removed. FOLLOW-UP: Thoracic radiography every 3 months to monitor for recurrence, Cure possible if tumor is surgically respectable, Prognosis is poor for patient with nonresectable thymoma. BEST PROTOCOL AT GULF COAST: In pets with nonresectable disease we use a combination of radiation (3 times per week for 6 weeks) and weekly Vincristine therapy. Afterwards, if deemed resectable on CT scan, we consider surgical removal. In these patients, we have >80% of cats and dogs survive with a good quality of life for >1 year. ______________________________________________________________________ For further information on "Thymoma" or about any other cancer issue, please call us (713-693-1166) or email Dr. Hahn at drhahn@gulfcoastvetspec.com . For more information on the web, use Medline at: ================================================================= Tumor Tidbits, April 2001. Volume 2, Number 5.