Abstract

A 14-year-old male African lion (Panthera leo) presented with lethargy and serous epiphora from the right eye. Clinical signs progressed over the next 5 weeks to include right unilateral enophthalmia, ptosis, mydriasis, atrophied temporal and masseter muscles, and intermittent epistaxis. Complete blood count and select sera chemistries did not reveal abnormalities. Rickettsial disease assays were negative. The 2M antibody test for masticatory muscle myositis was negative. Affected skeletal muscle biopsies revealed mild myositis and rhabdomyolysis. The lion became refractory to treatment and was humanely euthanized. Postmortem magnetic resonance imaging (MRI) of the head revealed an intracranial mass in the region of the right oculomotor and trigeminal nerves. Necropsy revealed masses in numerous organs. The intracranial mass was closely associated with the right oculomotor and trigeminal nerves. Histologic exam identified a disseminated spindle cell sarcoma. Immunohistochemical labeling was positive for smooth muscle actin, and the tumor was diagnosed as a metastatic leiomyosarcoma of undetermined tissue origin. Clinical signs were attributed to multisystem metastatic lesions rather than the primary tumor.

Acknowledgments

The authors would like to thank the animal care staff at the Kansas City Zoo for their care of the lion, Roy Brown of Histology Consulting Service for slide preparation, and Cathy Minogue of Northwest ZooPath for data retrieval.