Abstract

A 23-year-old female Atlantic bottlenose dolphin, Tursiops truncatus was diagnosed with squamous cell carcinoma of the oral cavity. She has a history of oral lesions, with the first noted on the tongue in 1987. In 1995 a raised lesion on her frenulum measuring 2.25 cm in diameter was observed. The lesion became chronic in nature and was slow growing. Cultures of the affected area were non-diagnostic and blood work was within normal limits. Serology panels for fungi and viruses were negative. Topical antibiotic ointments and systemic antibiotics had no effect on the mass. A needle aspirate performed in 1996 revealed inflammatory cells and the presence of an occasional spirochete. The mass at this time was 4.5 x 3 x 2 cm in diameter.

Biopsy was obtained with a harmonic scalpel (Ethicon Endosurgery, Cincinnati, OH) in 1999. At this time the tumor mass infiltrated the entire frenulum, deviating the tongue to the left. Histopathology revealed a medium grade, well-differentiated, malignant squamous cell carcinoma. Additional tissues were submitted for electron microscopy, PCR and immunohistochemistry. Radiographs were obtained of the chest, abdomen and mandible. The lung fields and abdomen appeared clear of metastasis and the mass did not infiltrate into the mandible.

The tumor was estimated to be 100 cu.cm. Due to its large size, location and vascularity, laser to surgically de-bulk the mass was used. The treatment plan was to perform laser surgery every 8-12 weeks for as long as necessary in an effort to control the tumor's growth. The dolphin was medicated with Versed and Meperidine in order to achieve adequate sedation and analgesia. Lidocaine was injected locally in and around the tumor and laser surgery was initiated using an Accuvet 810nm Diode laser (ESC Sharplan Medical Systems, 250 First Ave., Suite 300, Needham, MA 02494-2814). The tumor was partially de-bulked and a 2.5 x 3.5 x 1.5 cm section removed. The dolphin was placed on antibiotics 24 hours prior to surgery and continued for 10 days post-op. Eight weeks later a second laser surgery was performed. The dolphin handled both surgeries extremely well and recovery was uneventful. Following the second surgery, she was able to extend the tip of her tongue for the first time. However, tumor re-growth at the surgical site was rapid.

Chemotherapeutic agents were then instituted. An initial test dose of Carboplatin (Paraplatin) was injected intra-lesionally. Carboplatin was then administered at a dose of 1 mg per cu cm, of tumor. The dolphin recovered quickly following the procedure. Her behavior was normal, her appetite excellent, and she remained active and alert. Post operatively, moderate inflammation was observed. No significant abnormalities were evident in either the hematology or serum biochemistry. Intra-lesional chemotherapy was performed at a full dose of 100mg every two weeks for 6 more treatments.

Current tumor size is estimated at 41 cu cm. At this time the dolphin is doing extremely well. She continues to have an excellent appetite and attitude. She enthusiastically participates in research and training sessions and appears unaffected by the presence of the tumor. Blood work is normal except for an elevated sedimentation rate and lymphopenia. It is hypothesized that the tumor recruits lymphocytes into the area, thus fluctuating levels of lymphocytes are available in the blood.

Etiology of the squamous cell carcinoma is unknown but it is strongly suspected that a papillomavirus may be the etiology or a cofactor in the pathogenesis of this lesion. This speculation is based on preliminary molecular pathologic studies and similar lesions that have been found in other bottlenose dolphins. Studies to confirm this speculation are presently in progress.

The long-term treatment of this dolphin involves the continued use of intra-lesional chemotherapy. Chemotherapeutic agents will be rotated in order to avoid possible resistance. Adjuvant laser surgery will also be performed as needed. These treatment modalities should be considered for dolphins diagnosed with oral squam0us cell carcinoma that are considered refractory to conventional means of excision.

Acknowledgements

 Louis M. Herman, Adam A. Pack and Staff of KBMML/TDI

 Ruth Ewing, University of Miami

 Thomas P. Lipscomb, Armed Forces Institute of Pathology

 BarbPowers, Colorado State University

 Terry Campbell, Colorado State University

 KBMML/TDI Vet Med/Husbandry Interns: Becca Cowan, Beth Fletcher, Darlene Randles,

 Amanda Moore, Sarah Collyer-Brahm, Rachel Sherman, Jessica Benko, Annie Miller, Kelsey

 Abbott, Shannon Graham, Chris Imrich, Mike Belshaw