Abstract

An 11+-year-old, wild-caught, female Atlantic stingray (Hypanus sabinus) presented with an approximately 5 cm × 6 cm subcutaneous swelling in the pharyngeal region that extended into the oral cavity. The ray had a chronic history of pectoral fin cystic dermal nodules and parauterine cysts. The pharyngeal swelling was causing apparent dysphagia, leading to hyporexia and weight loss. Ultrasonography revealed a mixed echogenic encapsulated mass, and fine needle aspirate revealed unidentified mesenchymal cells. A biopsy was performed, and the mass was determined to be a spindle cell sarcoma with features suggestive of a nerve sheath tumor. Considering the associated weight loss and declining quality of life, we elected to attempt surgical excision of the mass despite the precarious location adjacent to the heart. The ray had done well under previous anesthetic procedures.

Surgery was performed on a recirculating table with the ray in dorsal recumbency. The ray was ventilated simultaneously via three methods due to the challenging location of the mass: tubing within the oral cavity, directly in the right and left fourth gill slits, and within both spiracles. The mass was excised via blunt dissection and bipolar radiosurgery. Hemorrhage was controlled with hemoclips. The mass was white to tan and had an irregular lobulated surface with soft to gelatinous areas. Nerve-like tissue was wrapped around one area of the mass and was not excised. The entire mass and the majority of the surrounding capsule were removed, followed by two-layer surgical site closure. Histology confirmed the previous spindle cell sarcoma diagnosis and a new finding of entrapped thyroid follicles. It was unclear whether the mass originated within the thyroid or was invading it. Post-operative treatments included antibiotics, analgesics, vitamins C and E, and tube feedings. The ray began eating three weeks post-operatively with subsequent weight gain, and the surgical incision healed without complication.

Seven months later, the ray presented with labored respiration and right spiracle swelling. Endoscopic gill exam revealed several adult monogenoids of the family Monocotylidae, which were treated with praziquantel immersion. Labored respiration recurred three months later. Gill cysts were noted, but no parasites were seen. Oral prednisone was initiated with initial improvement seen. The ray became refractory to treatment and was euthanized due to declining condition eleven months post-operatively. Necropsy revealed a stalk of tissue where the pharyngeal mass was removed, a cystic gill lesion, ulcerated gastric and intestinal mucosa, irregular kidneys, and a mass adjacent to the right kidney in the region of the interrenal gland. Histologically, the pharyngeal sarcoma did not recur, though the ray had a different neoplasm located in the interrenal gland—a presumptive carcinoma. In addition, there was focal granulomatous branchitis, chronic kidney disease, extensive mucosal hyperplasia with a monogenean in the pharynx, and chronic gastroenteritis. Various neoplasms have been documented in stingrays including lymphoid neoplasia and a hepatoblastoma in an Atlantic ray.^1-5 Our case highlights the successful removal of a large pharyngeal spindle cell sarcoma in a geriatric ray. Surgery should be considered in other rays with similar presentations.

Acknowledgements

The authors thank the New England Aquarium aquarists and biologists for their extremely diligent care of this animal and Dr. Stephen Bullard for identification of the gill parasite.

*Presenting author

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