Mammary gland tumors are common in dogs and cats but seldom found in bears.3,4 An 18-year-old female Malayan sun bear (Helarctos malayanus) with no breeding history in Taipei Zoo was discovered to have three 1×2 cm2 masses and one ulcerative lesion on the left abdomen in late 2006. Two mastectomy surgeries were performed to remove the masses and the mammary gland in January 2007.1 The masses were diagnosed as adenocarcinoma of the mammary gland and were considered metastasized by histopathologic examination. An incisional biopsy of an enlarged left axillary lymph node was performed later. Histopathologic examination revealed a sheet of vacuolated tumor cells with a high degree of atypia and nuclear pleomorphism. A complete blood count and serum biochemistry profile were within normal reference range, and radiologic films revealed no apparent metastasis to other organs. The human tumor markers for mammary gland tumors, CA 15-3 and CEA, which are thought to be helpful in clinical diagnosis,2 were detected in this case. Lymphadenectomy and ovariohysterectomy were later performed, and the bear has been in good health since the surgeries.
1. Andrew, N.C. 2003. Principles of treatment for mammary gland tumors. Clin Tech Small Anim Prac. 18:107–109.
2. Duffy, M.J. 2006. Serum tumor markers in breast cancer: are they of clinical value? Clin Chem. 52:345–351.
3. Stetter, E.C. 2003. Ursidae and Hyaenidae. In: Fowler, M.E., and R.E. Miller (eds.). Zoo and Wild Animal Medicine, 5th ed. WB Saunders, St. Louis, Missouri. 523–537.
4. Klein, M.K. 2007. Tumors of the female reproductive system. In: Withrow, S.J., and D.M. Vail (eds.). Small Animal Clinical Oncology, 4th ed. Saunders Elsevier, Canada. 619–636.