JPC SYSTEMIC PATHOLOGY

SPECIAL SENSES SYSTEM

April 2024

S-M10

 

Signalment (JPC Accession #2382810): A cat

 

HISTORY: Tissue from a cat with a history of dysphagia. Large, fleshy masses were present in the ear and underneath the tongue.

 

HISTOPATHOLOGIC DESCRIPTION: Oropharyngeal mucosa (per contributor): 

The submucosal connective tissue is expanded by abundant mature collagen interspersed with numerous small to medium caliber blood vessels which elevates the overlying mucosa, forming a polypoid projection. Within the submucosal connective tissue, there are multifocal small inflammatory aggregates composed of variable proportions of neutrophils, lymphocytes, plasma cells, and macrophages; increased clear space and dilated lymphatics (edema); and multifocal hemorrhage. The mucosa is predominantly composed of stratified squamous epithelium forming few papillary projections with rare areas lined by ciliated epithelium. The epithelium is multifocally ulcerated and overlain by a serocellular crust composed of eosinophilic and karyorrhectic debris (necrosis), eosinophilic fibrillar material (fibrin), and viable and degenerate neutrophils. There is subjacent granulation tissue. Elsewhere, mucosal epithelial cells are swollen with vacuolated cytoplasm (hydropic degeneration) and surrounded by transmigrating degenerate neutrophils.

 

MORPHOLOGIC DIAGNOSIS: Oropharyngeal mucosa (per contributor): Fibrovascular polyp, with chronic-active inflammation and ulceration, breed unspecified, feline.

 

CONDITION: Feline nasopharyngeal polyp, inflammatory aural polyp, aural inflammatory polyp, auditory inflammatory polyp

                             

GENERAL DISCUSSION: 

• Nasopharyngeal polyps of cats are non-neoplastic inflammatory masses arising within the middle ear or auditory tube that undergo expansile growth within the nasopharynx or the external ear canal
• Also occur in dogs and horses

 

PATHOGENESIS:

• Unknown; possible mucosal response to localized chronic inflammation, otitis media, or congenital defects
• Possible sites of origin: Middle ear mucoperiosteum, auditory tube mucosa, external ear epidermis/dermis

 

TYPICAL CLINICAL FINDINGS:

• Cats 1-3 years of age
• Extension of mass into the pharynx causes dyspnea, dysphagia, stridor, voice change, and gagging
• Nasal cavity involvement causes sneezing, nasal discharge, and epistaxis, mass may protrude through the nares
• Middle ear involvement causes ataxia, Horner’s syndrome, and/or facial nerve paralysis
• External ear canal involvement causes otomiasmic otorrhea (otoblennorrhea), otalgia, erythema, and head shaking
• Recurrence after excision via traction is common

 

TYPICAL GROSS FINDINGS:

• Moist, glistening and spherical, often pedunculated masses
• May remain in middle ear, evert through auditory tube on a thin stalk into the nasopharynx and displace the soft palate, or perforate the tympanic membrane and produce a visible mass within the external ear canal  

 

TYPICAL LIGHT MICROSCOPIC FINDINGS:

• Loose fibrovascular core covered by ciliated respiratory epithelium +/- squamous metaplasia, +/- ulceration
• Often accompanied by edema and mixed inflammatory infiltrates 
• Polyps originating from the middle ear or auditory tube nearly always contain pseudoglands lined by respiratory epithelium (including goblet cells)
• Polyps from the external ear (external acoustic meatus) are lined by squamous epithelium and may contain ceruminous or sebaceous glands but no pseudoglands 

 

DIFFERENTIAL DIAGNOSIS: 

• Inflammatory polyp of the nasal turbinates of cats (feline mesenchymal hamartoma): Another form of feline nasal polyp which arises from the nasal turbinate; consist of fibrous tissue with woven bone covered by ciliated epithelium 
• Idiopathic lymphoplasmacytic rhinitis in dogs and cats can create polypoid projections of nasal mucosa which obstruct nasal passages
• Tonsillar polyps occur rarely in dogs; unilateral pedunculated to sessile masses originating from the tonsils; have variable proportions of lymphatic vessels, fibrous or myxomatous or lipomatous stroma, and lymphoid tissue; most common subtype was lympangiomatous in a recent report (Molin 2021)
• Fungal granuloma (i.e. Cryptococcus neoformans in cats, Rhinosporidium seeberi in dogs)
• Neoplasia (i.e. pedunculated fibroma, papilloma, adenocarcinoma)

 

COMPARATIVE PATHOLOGY:

• Salmonella enterica ssp. diarizonae causes nasal polyps in sheep
• Nasal polyps arising from middle ear or auditory tube in other domestic species and are uncommon but also reported in sheep, horses, and dogs
• Hemorrhagic nasal polyps (progressive ethmoid hematoma, P-M08) are relatively common in horses and arise from the ethmoid turbinate region of the nasal cavity
• In dogs, nasal polyps frequently occur in conjunction with nasal carcinoma 

 

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. Philadelphia, PA: Elsevier Saunders; 2016:477-478.   
2. Lopez A, Martinson SA. In: Zachary JF, ed. Pathological Basis of Veterinary Disease. 7th ed. St. Louis, MO.; Mosby-Elsevier: 2022:567.

3. Molin J, Vilafranca M, Suarez-Bonnet A, Altimira J, Ramirez G. Canine Tonsillar Polyps: Characteristics, Classification, and Review of Pathogenesis. Vet Pathol. 2021; 58(1): 136-141.

4. Njaa BL: The Ear. In: Zachary JF, ed. Pathological Basis of Veterinary Disease. 7th ed. St. Louis, MO.; Mosby-Elsevier: 2022:1367-1368.

5. Njaa BL: Special Senses. In: Maxie MG, ed. Jubb, Kennedy and Palmers Pathology of Domestic Animals. 6th ed. Vol. 1. Philadelphia, PA: Elsevier-Saunders: 2016: 498-499.

6. Tarrant JC, Holt DE, Durham AC. Co-occurrence of nasal polyps and neoplasms of the canine nasal cavity. Vet Pathol. 2019;56(6):885-888.

 

 

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