"Digit Tumors" TUMOR TIDBITS, A BIWEEKLY VETERINARY ONCOLOGY E-LETTER Volume 3; Number 18; May 17, 2002. Editor: Kevin A. Hahn, DVM, PhD, Dipl - ACVIM (Oncology) & Overall Nice Guy! (drhahn@gcvs.com). ANNOUNCEMENTS 1 - Check our new and improved web site regularly for information on clinical trials and helpful hints: www.gcvs.com! 2 - We'll be in Dallas for the Annual Forum of the American College of Veterinary Internal Medicine the week of May 27th! THIS WEEK'S TUMOR TIDBIT: Digit Tumors OVERVIEW * Squamous cell carcinoma of the digit is the most common malignant tumor of the digit arising from the subungual epithelium. Others include melanoma, fibrosarcoma, mast cell tumor, and osteosarcoma. * Large breeds and black dogs are predisposed, particularly the standard poodle and Labrador retriever. * Median age is 10 years but digit tumors can occur in dogs as young as 4 years old. * Rare in cats SIGNS * Swelling of the digit is the reason for examination. * Ulceration in some animals * Multiple digits rarely affected * Lymph node and lung metastasis are reported but are uncommon at the time of examination. CAUSES AND RISK FACTORS * Cause unknown * Hereditary factors and black skin pigmentation are risk factors. DIFFERENTIAL DIAGNOSIS * Nail bed infection * Osteomyelitis DIAGNOSTIC RESULTS * Thoracic radiographs important to rule out metastatic disease; results typically normal at the time of diagnosis. * Radiographs of the affected foot reveal lysis of the third phalanx of the affected digit in 75% of patients. * Wedge biopsy of abnormal tissue required to confirm the diagnosis. TREATMENT * Amputation of the affected digit at the level of the metacarpal (or metatarsal) phalangeal joint the treatment of choice. FOLLOW-UP * If surgical excision is complete, and no evidence of metastatic disease is seen at the time of surgery, the 1- and 2-year survival rates for squamous cell carcinoma after amputation of the digit are 76% and 43%, respectively. For melanoma, 33% present with evidence of pulmonary metastasis and in those without obvious metastatic disease and digit amputation, the 1 year and 2 year survival rates are 42% and 13%, respectively. * Recurrence with complete excision is not anticipated. WHAT DO WE DO AT GULF COAST? * If the digit cannot be removed with the assurance of complete margins, we recommend the use of radiation (for squamous cell carcinomas, 3 per week for 7 weeks; for melanoma, once per week for 6 weeks) with a >80% chance of complete remission at the radiation site and a <10% for local tumor regrowth following irradiation. * If metastasis is suspected or treatment for metastasis is desired, we recommend the use of Carboplatin chemotherapy (for squamous cell carcinoma 300 mg/m2 IV every 3 weeks for 4 treatments; for melanoma 90 mg/m2 IV weekly for 6 weeks). * If chemotherapy is used for dogs with melanoma, the 1 year and 2 year survival rates are 50% and 40% respectively. I hope this "tidbit" helps, don't hesitate to call or email us at Gulf Coast Veterinary Oncology! Kevin Kevin A. Hahn, DVM, PhD Diplomate ACVIM (Oncology) & Overall Nice Guy Gulf Coast Veterinary Diagnostic Imaging & Oncology 1111 West Loop South, Suite 150, Houston, TX 77027 P: 713.693.1166 F: 713.693.1167 W: www.gcvs.com ****Please note that my new email address is drhahn@gcvs.com****