+ Etiology

• Tumors of nasal cavity represent approximately 1% of all tumors in dogs and less common in cats
• Etiologic factors include exposure to smoke, indoor kerosene or coal combustion and flea spray
• Sex predisposition in cats: male with a male-to-female ratio of 2:1
• Median age: 10 years although cats with non-epithelial tumors may present at an earlier age

+ Pathophysiology

• Nasal tumors are malignant in 91% cats
• 43% of nasal tumors in cats are epithelial (50% ADC and 50% SCC) and 28% LSA (71% B-cell, 17% epitheliotropic T cell, and 12% non-epitheliotropic T cell)
• 25%-40% of malignant tumors are sarcomas such as FSA, CSA, OSA, undifferentiated sarcoma, rhabdomyosarcoma, HSA, leiomyosarcoma, myxosarcoma, and malignant fibrous histiocytoma
• Nasal LSA is rare in both species, but more common in cats and not associated with FeLV infection
• Other round cell tumors include plasmacytoma, transmissible venereal tumor, MCT, and histiocytoma
• Other nasal tumors include malignant melanoma and paranasal meningioma
• Nasal tumors, regardless of histologic type, are characterized by locally invasive growth
• Metastatic rate is low at diagnosis but reported in up to 50% of dogs at necropsy
• Metastatic sites include lymph nodes and lungs ± bone reported in 2 dogs
• Benign nasal tumors include adenoma (19% of epithelial tumors in cats), basal cell tumor, fibroma, and neurofibroma
• Nasal vestibule is the most common site for feline nasal SCC, malignant melanoma, and basal cell tumor

+ General Considerations

• History, clinical signs, survey radiographs, CT, and tissue biopsy
• Hematology and clotting profile to exclude bleeding disorders: platelet count, PCV, ACT, PT, and APTT
• Lymph node aspirates are positive in 10% and thoracic radiographs are usually normal at presentation
• CSF should be collected if CNS involvement: increased CSF pressure, protein, and rarely cell count are abnormal

+ Clinical Signs

• Intermittent and progressive unilateral epistaxis ± mucopurulent discharge
• Other clinical signs: sneezing, reverse sneezing, stertorous respiration, dyspnea, facial deformity, epiphora, and neurologic signs (i.e., seizures, behavioural changes, and obtundation) due to direct invasion of cranial vault
• Mean duration of clinical signs prior to presentation is 3 months
• DDx: bleeding diathesis, hypertension, bacterial or fungal rhinitis, and developmental anomalies

+ Survey Radiographs

• Nasal radiographs determine extent of disease, presumptive diagnosis, and locate an area for biopsy
• Views: lateral, dorsoventral, frontal sinus, open mouth oblique, and open mouth ventrodorsal
• Radiographic pattern depends on histologic type, duration, and previous treatment
• Mixed pattern of conchal destruction ± increased soft tissue opacity
• Opacification of the ipsilateral frontal sinus is often due to impaired sinus drainage, but extension of the neoplastic process into the frontal sinus can also occur
• Less defined and more destructive appearance with aggressive nasal tumors
• Early neoplasia is difficult to differentiate from rhinitis
• Unilateral increase in nasal opacity with attenuation or obliteration of normal conchal pattern is characteristic of early epithelial nasal neoplasia
• Radiographic appearance becomes more heterogenous due to progressive conchal destruction with tumor progression and growth
• Nasal septum can be deviated or destroyed by neoplastic process, but this is difficult to assess
• Peripheral signs of nasal neoplasia includes soft tissue swelling, facial bone destruction, and periosteal new bone formation, and these signs are usually associated with highly aggressive neoplasms

+ Computed Tomography

• CT is preferred for determination of extent of disease and planning for radiation therapy
• Useful for determining extent of disease and involvement of cribriform plate and orbit

+ Biopsy

• Trans-nostril technique preferred for core biopsy although rhinoscopic and open techniques also used
• Techniques: punch biopsy, large-bore plastic cannula, curette, or grasping (i.e., melon ball) forceps
• Measure from the external nares to the medial canthus to prevent penetration of cribriform plate
• Mild resistance is usually discernible when tumor tissue is encountered
• Other techniques: nasal wash with fluid retrieval for cytologic examination (usually unrewarding), brush cytology (often non-diagnostic for mesenchymal tumors), and rhinoscopic biopsy (although samples are small and superficial)
• Complications: mild to moderate hemorrhage
• Hemorrhage is usually self-limiting but carotid ligation is occasionally required

+ Surgery

• Palliative
• Nasal neoplasia is usually advanced with bone invasion and critical location adjacent to eyes and brain
• Acute and chronic morbidity with dorsal rhinotomy
• No improvement in survival time with surgery compared to conservative management or surgery and radiation therapy compared to radiation therapy alone
• Principal indication for surgery is rostral nasal tumors (i.e., nasal planum and vestibule)
• Unilateral or bilateral carotid artery ligation may be required to control epistaxis

+ Photodynamic Therapy

• Photodynamic therapy has been used to treated 1 cat and 3 dogs with nasal tumors using pyropheophorbide-a-hexyl ether as the photosensitizing agent
• Photodynamic therapy is well tolerated with no cutaneous sensitization, but facial swelling is common and resolves within 72 hours
• Clinical signs are controlled for 2 weeks to > 54 weeks

+ External Beam Radiation Therapy

General Considerations

• CT is preferred for planning of radiation field and dosing to limit exposure of normal tissue
• Role of surgical debulking prior to radiation therapy is unknown
• Surgical debulking is required for orthovoltage but optional for cobalt and megavoltage radiation therapy
• Surgical debulking after curative-intent radiation therapy significantly improves survival time
• Dose: 18 fractions at 3 Gy per fraction for 54 Gy total dose
• Accelerated dose: 10 fractions at 4.2 Gy per fraction for 42 Gy total dose

Complications

• Oral mucositis, rhinitis, and radiation-induced moist desquamation for 4-8 weeks
• Treatment of oral mucositis includes tannic acid, glutamine (1.3 g/m 2 q 8 hrs PO), and benzydamine
• Ocular changes (i.e., KCS, corneal ulcers, and cataracts) if eyes included in radiation field and dose > 40 Gy

+ Brachytherapy

• Intracavitary therapy using radioactive isotopes
• Potential problems include dose distribution and radiation exposure to personnel

+ Nasal Lymphosarcoma

• MST 1,397 days for cats with nasal LSA treated with radiation therapy alone
• MST 151 days for cats with nasal LSA treated with chemotherapy alone
• MST 337 days for cats with nasal LSA treated with radiation therapy and chemotherapy, with a 12-month survival rate 46%

+ Other Nasal Tumors

Mean survival time 382 days to 19 months for cats with non-LSA nasal tumors treated with radiation therapy alone, with 1-year survival rate 44%-63% and 2-year survival rate 17%