Abstract
In 2017, an adult female swell shark (Cephaloscyllium ventriosum) originally presented for rupture of the left globe. Medical management was initially elected, and the eye was treated with oral antibiotics until the perforation closed with suspected scar tissue. Over the next few years, the globe continued to remodel with suspected scar tissue, and there were intermittent episodes of increased inflammation of the globe which were also managed with antibiotics. In 2019, the left globe was noted to be markedly enlarged and appeared as a white, irregular, firm mass. Surgical management was elected, and enucleation was performed. Over the next year, the enucleation site healed poorly with persistent, non-healing wounds at both ends of the incision site.
In June of 2020, the shark presented with intermittent symptoms of vestibular disease, including flipping into dorsal recumbency, then correcting the abnormal posture. A 3 by 5 cm soft, subcutaneous mass was also noted just caudal to the right pectoral girdle near the base of the right pectoral fin. Cytologic examination of a fine needle aspirate was consistent with an inflamed cyst. The shark was empirically treated for presumed meningitis/encephalitis with antimicrobial and anti-inflammatory drugs. Over the next 3 months, the shark developed progressive vestibular signs, including persistently bending its body to the left, inverting its body, and resting in dorsal recumbency. Euthanasia was elected for humane and diagnostic purposes.
At necropsy, a tan, irregular mass 10 cm in greatest dimension infiltrated the musculature overlying the right pectoral girdle and extended along the body wall to the umbilical scar. An approximately 5 cm, white, firm multinodular mass partially filled the left orbit. This mass tracked deep along the optic nerve and communicated with a mass in the left side of the brain. Histologic analysis identified the brain lesion as a poorly differentiated spindle cell sarcoma present in the meninges and neuropil of the brainstem and midbrain. Metastases were identified in the musculature and skin of the right body wall, the gills, and an olfactory mucous membrane. Histologic findings most closely resembled a malignant meningioma.
Metastatic neoplasia is rare in elasmobranchs. While this is not the first instance of a spindle cell tumor in a swell shark1 and there is one other citation in the literature of a benign central nervous system tumor in a shark,2 to the authors’ knowledge, this is the first reported instance of a primary malignant central nervous system tumor with metastatic spread in an elasmobranch3,4.
Acknowledgments
The authors wish to thank the Cabrillo Marine Aquarium staff for their dedicated care of this animal and for their collaboration. The authors also wish to thank the Aquarium of the Pacific for support of this project through the veterinary student externship program.
*Presenting author
+Student presenter
Literature Cited
1. Berzins IK, Hovland E. 1999. Shark tumor: an oxymoron. In 30th Annual International Association for Aquatic Animal Medicine Conference and Workshop, Tampa, FL; p. 3–7.
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3. Harshbarger JC. 1999 (pers. comm.). Registry of Tumors in Lower Animals. Department of Pathology, George Washington University Medical Center, Washington, DC.
4. Stoskopf MK. 1993. Neoplasia in sharks. In: Stoskopf, M.K., editor. Fish Medicine. W.B. Sanders Company, Philadelphia, PA, p. 808–809.