Abstract

A 37-year-old wild caught female dolphin with a history of chronic, non-healing ulcerated lesions on the tongue and frenulum was diagnosed with oral squamous cell carcinoma in July 2005. While most of the lesions remained 1-2 mm in size, one area in the sublingual tissue ventral to the left side of the tongue developed an ulcerated fissure and formed into a palpable mass. This animal became pregnant in May of 2005 and we observed a significant and more rapid increase in the size of the mass during the pregnancy. This was likely a result of a pregnancy related decrease in her immune status.¹ The pregnancy also limited our treatment efforts because we did not want to beach or restrain the animal in the later stages of the pregnancy.

Several modalities have been used to treat oral SCC in the dolphin including surgical lasers^2,3, intra-lesional chemotherapy⁴, brachytherapy⁵, cryosurgery and standard surgical excision.⁶ Multiple cryosurgical procedures failed to impede the growth of this lesion, so the decision was made to perform a radical surgical excision of the estimated 140 cm³ affected area. Approximately two weeks prior to the procedure, a CT scan was performed in an attempt to map out the boundaries of the lesion and to look for evidence of metastasis in the lungs. This modality was not ideal for discriminating between the affected and unaffected sublingual tissues. However, we were able to determine that there were no gross metastatic lesions visible in the lung fields.

The surgical procedure took place in September 2006 and lasted 2 hours and 45 minutes. The dolphin was premedicated with a 30 mg oral dose of diazepam. Regional and local anesthesia was utilized during the procedure. Inferior alveolar nerve blocks were performed by bilaterally injecting 5 ml of 2% Lidocaine at the mandibular foramen. The sublingual tissue was also infused with 2% lidocaine at each area prior to incision or surgical manipulation of the tissues. Approximately 3-5 ml of lidocaine were injected at multiple sites throughout the procedure for a total dose of 40 ml. An additional 10 mg dose of diazepam was administered IM approximately 1.5 hours into the procedure.

The mass was removed in 5 sections, with the later 4 done in an attempt to get clean margins. Hemostasis was controlled with electrocautery (Bovie), electroligation (Ligasure) or by ligation with 3-0 Silk. A two-layer closure was done on the submucosal tissues using 3-0 and 4-0 Biosyn. 4-0 Monocryl was used to appose the mucosa using a continuous subcuticular pattern. We were unable to appose the mucosa at the caudal end of the incision, so a 2.5 cm section was left to heal by second intention.

Post-operatively, the dolphin did very well. She received 100 mg carprofen IM after the procedure and orally once daily for the next 2 days, after which she received this dose every other day for 2 doses. She also continued on enrofloxacin, which she had started receiving 48 hours prior to the surgery. The wound was flushed and debrided 4 times per day with a 50% vinegar solution. The incision healed unremarkably and follow-up cryosurgical procedures have been performed to address the remaining pinpoint lesions. We are monitoring for recurrence along the incision line, but so far no gross lesions have been observed.

References

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2.  Dover S. Laser as a treatment for squamous cell carcinoma in a Pacific white-sided dolphin. Abstr. Proc. IAAAM. 1994 Pp. 145.

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4.  McKinnie CJ, Dover SR, Bossart GD, Olgilvie G. Treatment of oral squamous cell carcinoma in Atlantic Bottlenose dolphin (Tursiops truncatus). Abstr. Proc. IAAAM. 2001 Pp 37-38.

5.  McKinnie CJ, Dube S, Fitzgerald RB, Conant J, French B, Lederer JL. Permanent I-125 seed implant in the treatment of squamous cell carcinoma in an Atlantic bottlenose dolphin, Tursiops truncatus. Abstr. Proc. IAAAM. 2005 Pp. 71-72.

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