Abstract

A 39 year old female Atlantic bottlenose dolphin (Tursiops truncatus) demonstrated multifocal sublingual mucosal ulceration and proliferation in early 2006. The ulcers began bilaterally along the linear folds of the floor of the mouth and progressed longitudinally from the frenulum rostral to the cranial third of the intermandibular region. Excisional biopsies revealed friable multifocal ulcerative stomatitis with squamous cell transformation from carcinoma in situ to squamous cell carcinoma (SCC). Approximately 90% of the lesions were removed in two separate surgical procedures in June and July 2006. Post-operatively, cryotherapy, topical 5-Fluorouracil and systemic retinoid therapy (Acitretin) were used to slow disease progression. However, excisional biopsies taken in 2008 and early 2009 demonstrated that the neoplastic lesions were beyond surgical control. Radiation therapy using external beam photon radiation in six treatment fractions was performed weekly over the course of 8 weeks at the California Veterinary Specialists Angel Care Cancer Center. The dolphin was premedicated with oral diazepam (0.25 mg/kg) three hours prior to transport to the facility and additional sedation with intramuscular Midazolam (0.045 mg/kg) was administered 30 minutes prior to the procedure. The dolphin was positioned for the treatments on a modified hydraulic lift table and received approximately 2-3 minutes of applied radiation, receiving a total radiation dose of 40 gray. The radiation doses appeared safe as the therapy caused only mild local mucositis. At no point were changes in appetite observed. To this date, only mild sublingual ulceration exists while post-radiation tissue healing continues.

Acknowledgements

The authors would like to thank Keith Yip (SWC Curator of Mammals) and the SeaWorld Animal Training and Animal Care staff for their logistical assistance and husbandry. Also, special thanks to Drs. Kevin Brumund and William Read from UCSD Moores Cancer Center in La Jolla, California, for additional consultation on this case.