Neoplasia, Nasal and Paranasal
Tumors of the nasal passage and paranasal sinuses are uncommon and include a wide range of tumor types, reflecting the diverse tissues present in the head. Squamous cell carcinoma (SCC) is the most commonly diagnosed sinonasal tumor. Paranasal tumors are more common than nasal tumors. Most tumors are unilateral in occurrence.
• Secondary paranasal sinusitis is common with primary neoplasia of the sinuses because of disruption of normal sinus drainage mechanisms and the presence of necrotic tissue and secondary bacterial infection.
SCC, adenoma, adenocarcinoma, lymphoma, chondrosarcoma, fibroma, fibrosarcoma, osteoma (hamartoma), osteosarcoma, fibro-osseous tumors (fibrous dysplasia and ossifying fibroma), undifferentiated carcinomas and sarcomas, tumors of dental origin (eg, ameloblastoma), hemangioma, melanoma, mast cell tumor
• Most sinonasal tumors are slowly growing with an insidious onset of clinical signs. Horses typically have a history of developing nasal discharge (mucoid to purulent; maybe bloody) that persists and perhaps has a foul odor.
Nasal discharge: Malodorous, mucoid to purulent, and often bloody; unilateral or bilateral; reduced nasal airflow; increased respiratory noise localized to the nasal passage; dyspnea; external facial swelling (frontal and maxillary regions) is common with advanced disease; enlarged submandibular lymph nodes; epiphora; exophthalmos; ocular discharge; neurologic deficits; halitosis; dysphagia; inappetence.
• The frontal and ethmoidal sinuses have a greater density of mucosal glands, which may account for the increased incidence of glandular epithelial tumors in these locations compared with other sinus regions.
• Distant metastasis is rare; in addition to locally invasive and destructive growth, carcinomas frequently spread to other sites in the head (nasopharynx, oropharynx, periorbital, cranium, guttural pouch), resulting in diverse clinical signs.