Clinical features, MRI findings and outcome of a primary extranodal B-cell lymphoma affecting the tympanic bulla treated with chemotherapy alone.

Case summary: A 2-year-old neutered female feline leukaemia virus (FeLV)-negative domestic shorthair cat was referred with an acute onset of vestibular signs. A clinical examination identified evidence of otitis externa of the right ear and enlargement of the right mandibular lymph node. MRI revealed predominantly T2 and FLAIR hyperintense and contrast-enhancing lesions affecting the right external ear canal, tympanic bulla and nasopharyngeal regions with intracranial extension. Cytology and culture and sensitivity samples collected from the middle ear via myringotomy revealed a population of intermediate to large lymphocytes consistent with lymphoma and mixed Staphylococcus chromogenes and Pasteurella species infection. PCR for antigen receptor rearrangements on the ear cytology was consistent with a B-cell rearrangement. A primary extranodal B-cell lymphoma affecting the tympanic bulla and other sites with secondary septic otitis media and interna was diagnosed. After the improvement of clinical conditions after corticosteroid, antibiotic and chemotherapy treatment, the cat was alive 22 months after diagnosis without recurrence of clinical signs.

Relevance and novel information: This is the first report of a primary extranodal B-cell lymphoma affecting the tympanic bulla with suspected involvement of the nasopharynx and cranial vault treated with chemotherapy alone in the veterinary literature. Although very rare, B-cell lymphoma should be included in the differentials for diseases affecting the inner and/or middle ear and extending intracranially in cats. Chemotherapy represents a non-invasive treatment modality with a survival of up to 22 months appearing possible.