6-Year-Old Thoroughbred Gelding

Signalment & History

  • This patient presents for a 3.5 week history of bilateral epistaxis.
  • On physical examination, his vitals are normal. Moderate right sided exophthalmos is seen. There is a small amount of nasal discharge in the right nare.



There is a rounded, well-defined, soft tissue mass, with multiple mineral opaque foci located at the level of the right maxillary molars, in the region of the right caudal maxillary sinus. This mass extends into the right conchofrontal sinus, right rostral maxillary sinus, right nasal cavity, causing left sided deviation of the caudal portion of the nasal septum. The soft tissue mass causes right exophthalmos


  • Right sided neoplasia such as squamous cell carcinoma with maxillary obstructive sinusitis or ethmoid hematoma.


Equine nasal and paranasal sinus tumors

  • Equine nasal tumors are rare and are generally advanced at the time of diagnosis
  • Main classification of nasal tumors

1.Tumors of the surface epithelium

  • Squamous cell (epidermoid) carcinoma – most common
  • Spindle cell carcinoma
  • Transitional (intermediate) carcinoma

2.Tumors of glandular epithelium

  • Adenocarcinoma: highly locally invasive, frequently met to lymph nodes

3.Undifferentiated (anaplastic) carcinoma

  • Other tumors: fibrosarcoma, myxoma/myxosarcoma, hemangioma/hemangiosarcoma, lymphoma, mast cell tumor, osteoma/osteosarcoma, fibrous dysplasia, chronic ossifying fibroma
  • Predisposition for squamous cell carcinoma and unspecified carcinoma/sarcomas to develop in the maxillary sinus; adenocarcinomas predisposition for nasal and ethmoid regions
  • Tumors occur more frequently in the paranasal sinuses than in the nasal cavity
  • Sinonasal tumor-like lesions

1.Epidermal inclusion cysts (atheromas)

  • 2-5cm soft swelling in the nasal diverticulum of young horses

2.Maxillary cysts (sinus cysts)

  • Dermoid cysts
  • Dental residue cysts
  • Cysts lined by respiratory epithelium

3.Progressive ethmoid hematoma

  • Most cases 7+ years old, Arabian and Thoroughbred horses
  • Most lesions in ethmoid, but can be found in maxillary/frontal/sphenopalatine sinuses
  • May result in secondary fluid accumulation within the sinuses because of physical obstruction of normal drainage of the sinus cavities


  • Polyps: can be result of hyperplasia of mucosa or associated lymphoid tissue (inflammatory or allergic in origin)
  • Granuloma: Progressively destructive masses containing bone fragments from eroded conchae. May be caused by Staphylococci or Streptococci

5.Osteodystrophia fibrosa

  • Nutritional disease with thickening of the mandible, maxilla, conchae, etc.
  • Caused by diets with calcium to phosphorus ratios greater than 1:3