JPC SYSTEMIC PATHOLOGY

RESPIRATORY SYSTEM

SEPTEMBER 2023

P-M08

 

SIGNALMENT (JPC #4116504): A 14 year-old Arabian gelding

 

HISTORY: This horse had a long history of an upper airway issue with recent onset of a left-sided bloody, foul smelling nasal discharge. He displayed mild inspiratory noise that would progress to inspiratory stridor with respiratory difficulty when excited and had no airflow out of the left nostril. A CT and sinus endoscopic exam confirmed an expansile soft tissue mass within the left paranasal sinuses that deviated the nasal septum and originated from the ethmoid concha.

 

HISTOPATHOLOGIC DESCRIPTION: Nasal mucosa and submucosa, left ethmoid turbinate: The submucosa is expanded and the mucosa is elevated by a polypoid mass composed of variably loose to dense fibrous connective tissue interspersed with many small caliber blood vessels lined by plump, reactive endothelial cells (hypertrophy), numerous macrophages and multinucleated giant cells (both foreign body and Langhan’s type), and moderate numbers of neutrophils, lymphocytes, and plasma cells admixed with multifocal variable hemorrhage, eosinophilic beaded to fibrillar material (fibrin), and increased clear space (edema). Many macrophages and some multinucleated giant cells contain abundant golden-brown to bright yellow granular pigment (hemosiderin and hematoidin, respectively), and there are large, extracellular, up to 100µm in diameter lakes of yellow globular hematoidin pigment (ceroid sequins). Multifocally, collagen fibers of the submucosa and the tunica adventitia have increased basophilia (mineralization). Multifocally, the overlying respiratory epithelium is moderately thickened (hyperplasia) or lost (ulcerated). Multifocally, nasal glands are dilated or ectatic with attenuated epithelium and eosinophilic globular to flocculent material within the lumina (secretory product).

 

MORPHOLOGIC DIAGNOSIS: Nasal mucosa and submucosa, left ethmoid turbinate: Polyp, fibrovascular, with fibrosis, hemorrhage, mineralization, epithelial hyperplasia and ulceration, granulomatous inflammation, hemosiderosis, and hematoidin deposition (ethmoid hematoma), Arabian, equine.

 

CONDITION: Ethmoid hematoma

 

SYNONYMS: Progressive hematoma; progressive ethmoid hematoma (PEH); hemorrhagic nasal polyp

 

GENERAL DISCUSSION:  

• Usually occurs in older horses; Thoroughbreds and Arabians more commonly affected
• Recurrence following surgical excision is common

 

PATHOGENESIS:  

• Cause is unknown; they are assumed to result from an aberrant vasoproliferative response to submucosal hemorrhage
• Growth arises from submucosa of ethmoid tubinates; usually unilateral
• Can fill ipsilateral nasal meatus or grow into maxillary sinus

 

TYPICAL CLINICAL FINDINGS:

• Chronic, progressive, often unilateral epistaxis
• Slight epistaxis/nasal discharge at the affected nostril for weeks to years before presentation is the most commonly reported clinical sign
• Abnormal inspiratory and expiratory noise at exercise; coughing; episodes of choking; hypersalivation; slight bulging of facial bones over the paranasal sinuses; malodorous breath; head shyness; head shaking

 

TYPICAL GROSS FINDINGS:  

• Usually smooth-surfaced and soft; range in color from off-white to pink, red, brown, green, or purple  
• As mass grows, it often protrudes into surrounding paranasal sinuses and may extend rostrally into the nasal cavity towards the nostrils and caudally into the nasopharynx
• May cause distortion and necrosis of turbinates
• Capsule may be ulcerated or inflamed from secondary bacterial infection

 

TYPICAL LIGHT MICROSCOPIC FINDINGS:  

• Organizing hemorrhages of various ages and well vascularized stromal tissue with hemosiderin-laden macrophages and multinucleated giant cells
• Yellow to golden round globules of hematoidin (ceroid sequins)
• Mineralization of connective tissue and vessel walls 
• Epithelium may be ulcerated with a submucosal capsule of fibrous tissue

 

DIFFERENTIAL DIAGNOSIS: 

• Neoplasia of paranasal sinuses or nasal passages
• Other diseases that can cause bloody nasal discharge:
  1. Guttural pouch mycosis (Aspergillus nidulans)
     • In severe cases this can result in thrombosis, aneurysm formation, and rupture of the internal carotid artery
     • Tends to be isolated episodes of profuse epistaxis if the first episode is not fatal
  2. Fungal granulomas
  3. Nasal amyloidosis
  4. Paranasal sinusitis
  5. Facial bone fractures

 

COMPARATIVE PATHOLOGY:  

• Nasopharyngeal polyps in cats are common in kittens and young adults and commonly arise from the middle ear or auditory tube (S-M10)
• Nasal polyps in other domestic species are uncommon

 

REFERENCES:  

1. Caswell JL, Williams KJ. Respiratory system. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. Vol 2. 6th ed. St. Louis, MO: Elsevier; 2016:477.
2. Lopez A, Martinson SA. Respiratory System, Thoracic Cavities, Mediastinum, and Pleurae. In: Zachary JF, ed. Pathologic Basis of Veterinary Disease. 7th ed. St. Louis, MO: Elsevier; 2022:567, 599.
3. Pascoe JR. Ethmoid hematoma. In: Smith BP, ed. Large Animal Internal Medicine. 5th ed. St. Louis, MO: Mosby; 2015:561-562.
4. Wilson DW. Tumors of the respiratory tract. In: Meuten DJ, ed. Tumors in Domestic Animals. 5th ed. Ames, IA: Iowa State Press; 2017:474.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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