Gingival squamous cell carcinoma in 2 lions under managed care

Abstract

Neoplasia is one of the main causes of euthanasia in geriatric captive nondomestic felids. However, few studies have examined oral tumors in these animals. We describe here the clinicopathologic features of gingival squamous cell carcinoma (SCC) in 2 lions (Panthera leo) from separate zoologic collections. In both cases, the lions had a history of sialorrhea, bloody oral discharge, and anorexia. Autopsy findings in both lions were similar and were characterized by poorly circumscribed, friable, and bloody gingival masses with grossly apparent invasion of the mandibular bone; a pathologic fracture was observed in 1 case. Histologically, the masses consisted of poorly circumscribed, unencapsulated, densely cellular proliferations of neoplastic epithelial cells arranged in irregular islands, cords, and anastomosing trabeculae with formation of keratin pearls, which, coupled with positive immunohistochemistry for pancytokeratin, were diagnostic for SCC. Although no metastases were found in either animal, both lions were ultimately euthanized because of poor prognosis.

Keywords: Panthera leo; lions; neoplasia; oral pathology; squamous cell carcinoma.

Figure 1.

Gingival squamous cell carcinoma in 2 lions. A. A 15 × 10 × 7.0-cm, firm, hemorrhagic, and ulcerated white oral mass adjacent to the left lower canine and incisor teeth of lion 2 (L2). B. The left mandibular canine and incisors in L2 are loose, and the neoplasm infiltrates into and deforms the mandibular shape. C. A nonencapsulated mass composed of anastomosing cords and nests of neoplastic keratinocytes infiltrates and effaces collagen fibers in the gingiva of lion 1 (L1). H&E. D. Neoplastic keratinocytes in L1 have moderate anisocytosis and anisokaryosis. H&E. E. Proliferation of markedly pleomorphic keratinocytes in L1 arranged in solid nests and supported by moderate-to-abundant fibrovascular stroma. Centrally, some nests contain keratin pearls. H&E. F. Neoplastic cells in L2 have strong cytoplasmic immunoreactivity for pancytokeratin.