Perivertebral B-cell lymphoma in a Queensland koala (Phascolarctos cinereus adustus) with paralytic symptoms in the hind limbs.

A male Queensland koala (Phascolarctos cinereus adustus) at Kanazawa Zoological Gardens (Kanagawa, Japan) exhibited paralytic symptoms in the hind limbs. Computed tomography and magnetic resonance imaging revealed a mass on the left ventral side of the 11th to 13th thoracic vertebrae, and the presence of myelitis or edema in the spinal cord. The koala was under anesthesia during the examination and suddenly developed ventricular fibrillation and died. Necropsy revealed a firm flat ovoid hemorrhagic mass on the vertebrae. Following a microscopic examination including immunohistochemistry, the perivertebral mass was diagnosed as B cell lymphoma. Therefore, neoplastic cell infiltration into the spinal cord may cause paralytic symptoms in the hind limbs.