A relatively high incidence of neoplasia has been historically noted in marsupials, and in dasyurid marsupials in particular.2–5,8 Neoplasms noted in kowari (Dasyuroides byrnei) have included a schwannoma,6 a thoracic fibrosarcoma,2 a cerebellar medulloblastoma,2 a glossal squamous cell carcinoma (SCC) with pulmonary metastases,1 and SCC of the face (one case) and pinna (one case).3 Squamous cell carcinoma has also been noted in other dasyurids, including the Tasmanian devil (Sarcophilus harrisii),3-5,7 the tiger quoll (Dasyurus maculatus),3,9 the eastern quoll (Dasyurus viverrinus),3,8 the northern quoll (Dasyurus hallucatus),3 the common planigale (Planigale maculata),3 the fat-tailed dunnart (Sminthopsis crassicaudata),3 and the brown antechinus (Antechinus stuartii)3. This report describes several additional cases of SCC in kowari, usually originating from oral gingiva.
Between October 1997 and July 2000, twelve kowari from three zoologic institutions were diagnosed with SCC out of approximately 24 case submissions (50%). Ten kowari were euthanatized, and of these, eight were euthanatized primarily because of the neoplasm. Four had antemortem diagnosis by biopsy, which was later confirmed on necropsy. Eleven carcinomas were within the oral cavity: five arose from the maxillary gingiva, five from the mandibular gingiva, and one from the mucocutaneous junction at the oral commissure. A single lesion arose from a ceruminous gland at the base of the ear. Oral neoplasms usually presented as rapidly growing mandibular or maxillary masses, usually surrounded the molars, and were multilobulated, tan, and firm. Metastasis was not observed in any case; however, the lesions were locally aggressive with consistent invasion of surrounding osseous and soft tissues; and occasional invasion of the nasal cavity, nasolacrimal gland, tongue, or teeth. Loss of teeth and dental calculus/gingivitis of remaining ipsilateral teeth and the apposing arcade was frequently observed. Concurrent gingival hyperplasia was noted in three cases and was papillomatous in one of these cases. Of the affected kowari with known lineages, most had at least one affected parent.
Factors leading to this common neoplasm in this species may include genetic/familial disposition, viral infection such papillomavirus, or chronic gingivitis leading to neoplastic transformation. The observed gingival hyperplasia may represent a preneoplastic lesion in this species.
We thank Dr. Michael Briggs, Dr. Jennifer Langan, Dr. Thomas Meehan, and Dr. Jacqueline Zdziarski (Brookfield Zoo); Dr. Lucy Spelman, Dr. Jodie Sherrill, Dr. Becky Yates, Dr. Don Nichols, and Dr. Richard J. Montali (Smithsonian National Zoological Park); Dr. Stephanie James and Dr. Janet C. Martin (Roger Williams Park Zoo) for case submissions; R. Brown from Northwest ZooPath for assistance with pathology, and Jane Chladny and the University of Illinois College of Veterinary Medicine Histology Laboratory.
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