Bilateral cranial polyneuropathy associated with an intracranial mass in a cat with concurrent tonsillar lymphoma

A 14-year-old spayed female Siamese cat was presented with signs consistent with a rapidly progressive cranial polyneuropathy. Magnetic resonance imaging of the brain revealed an extra-axial mass at the calvarial floor, extending caudally to involve bilateral trigeminal nerves and rostrally to involve the pituitary gland and optic chiasm. Additional findings included contrast-enhancing content within the bilateral tympanic bullae, mild mandibular and medial retropharyngeal lymphadenopathy, and a left tonsillar mass. Cytologic and histopathologic findings confirmed tonsillar lymphoma. The concurrent intracranial mass and the middle ear content were presumed to represent the same disease process, but the diagnosis was not confirmed. Oral glucocorticoid and lomustine were effective in resolving the dropped jaw and facial hypoesthesia. Neurogenic dry eye and corneal hypoesthesia also improved gradually, leading to complete resolution of secondary bilateral corneal ulcers by 20 wk after initiation of the oral chemotherapy. The cat remained in clinical remission throughout this period and survived for 166 d after the diagnosis. This is the first report of tonsillar lymphoma without oropharyngeal clinical signs in a cat presented with signs suggestive of concurrent intracranial involvement, leading to a rapidly progressive bilateral cranial polyneuropathy. Key clinical message: Lymphoma should be considered as an important differential diagnosis in cats with cranial polyneuropathy. Feline tonsillar lymphoma can exhibit concurrent central nervous system involvement without detectable disease in other organs.