Nasopharyngeal eosinophilic sclerosing fibroplasia in a 15-year-old cat: expanding the anatomical and age spectrum of the disease.

Case summary: A 15-year-old, spayed female domestic shorthair cat was evaluated for chronic progressive stertor, mucopurulent nasal discharge and intermittent apnoeic episodes. CT revealed a soft tissue mass occupying the nasopharynx and partially obstructing the choanae. Nasopharyngoscopy confirmed a firm, pale, multilobulated lesion. Partial endoscopic debulking of the mass was performed, although further sampling was limited by post-procedural haemorrhage. Histopathology demonstrated dense eosinophilic inflammation with marked sclerosing fibroplasia, consistent with feline eosinophilic sclerosing fibroplasia (FESF); no histological features suggestive of lymphoma, carcinoma, fungal disease or inflammatory polyps were identified. Prednisolone was initially administered to minimise the risk of post-procedural inflammatory nasopharyngeal stenosis and subsequently continued for 31 days after histological confirmation of FESF. Two months later, CT and nasopharyngoscopy demonstrated complete anatomical resolution with full remission of clinical signs. Relevance and novel information: Nasopharyngeal involvement of FESF has not previously been reported; the condition is typically described in young to middle-aged cats with gastrointestinal disease. More recent reports describe its possible lymph node localisation in sites beyond the abdominal cavity. This case documents a geriatric-onset, extra-gastrointestinal presentation mimicking neoplasia or granulomatous disease. Diagnosis was achieved on biopsies obtained during partial debulking, and follow-up investigations confirmed complete anatomical resolution. This case expands the recognised anatomical and age spectrum of FESF and supports consideration of this entity in the differential diagnoses for nasopharyngeal masses in cats.