+ Etiology

  • Tumors of nasal cavity represent approximately 1% of all tumors in dogs
  • Etiologic factors include:
  • Dolichocephalic breeds
  • Dogs living in an urban environment
  • Exposure to smoke, indoor kerosene or coal combustion and flea spray
  • Sex predisposition in dogs: ± male
  • Medium to large sized dogs are more commonly affected
  • Median age: 10 years although dogs with sarcomas may present at an earlier ag

+ Pathophysiology

  • Nasal tumors are malignant in 80% dogs
  • 60%-75% of malignant tumors in dogs are carcinomas with ADC the most common while others include SCC, undifferentiated carcinoma, TCC, and neuroendocrine tumors
  • 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

alt text From: Withrow SJ & MacEwen EG (eds): Small Animal Clinical Oncology (3rd ed).

  • 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, 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

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+ 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

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+ 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

alt text From: Withrow SJ & MacEwen EG (eds): Small Animal Clinical Oncology (3rd ed).

  • 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

  • Clinical Staging


+ 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

+ Chemotherapy and Immunotherapy

  • No improvement in survival time
  • 27% response rate to cisplatin but MST only 20 weeks
  • OPLA-cisplatin is a radiation sensitizer and improves survival when used in combination with radiation therapy

+ 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


  • 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


+ General Considerations

  • MST 3-6 months for surgery, chemotherapy, immunotherapy, cryosurgery, and no treatment
  • MST 8-23 months for radiation therapy ± surgical debulking, with
  • 1-year survival rate 37%-81%
  • 2-year survival rate 10%-48%
  • MST 580 days for nasal tumors treated with radiation therapy and OPLA-cisplatin (v 325 days in historical group)
  • CSA respond better to radiation therapy than other nasal tumors
  • ADC responds better to radiation therapy than SCC or undifferentiated carcinomas
  • MST 165 days for non-keratinizing nasal SCC
  • Solid ADC may have a better prognosis than diffuse ADC

+ Prognostic Factors

  • Poor prognostic factors for nasal tumors treated with radiation therapy:
  • 10 years (MST 6.8 months v 10.4 months)

  • Facial deformity (MST 133 days v 402 days)
  • Regional lymph node or pulmonary metastasis (MST 109 days v 393 days)
  • Modified tumor stage II (MST 7.0 months v 17.2 months)
  • Radiation therapy not included in the treatment protocol (MST 126 days v 424 days)
  • Radiation total dose > 55 Gy (MST 7.1 months v 10.1 months)
  • Lack of resolution of clinical signs after radiation therapy (MST 133 days v 476 days)

+ Type of Radiation Therapy

  • Megavoltage radiation therapy is preferred for the treatment of nasal tumors in dogs
  • Cobalt radiation therapy is associated with a significantly worse outcome compared to orthovoltage radiation therapy (MST 7.6 months v 18.0 months)


I Ipsilateral tumor with no or minimal bone destruction
II Bilateral tumor with moderate bone destruction
III Bilateral tumor with extranasal extension
I Ipsilateral tumor with no or minimal bone destruction
II Bilateral tumor with moderate bone destruction
III Bilateral tumor with extranasal extension
Authors Radiation Type MST 1-Year Surv Rate 2-Year Surv Rate
Thrall & Harvey, JAVMA, 1983 Orthovoltage 23 months 57% 48%
Adams et al, JAVMA, 1987 Orthovoltage 8.1 months - -
Evans et al, JAVMA, 1989 Orthovoltage 16.5 months 54% 43%
Northrup et al, JVIM, 2001 Orthovoltage 7.4 months 37% 17%
Adams et al, JAVMA, 1987 Megavoltage 8.1 months - -
McEntee et al, Vet Radiol, 1991 Megavoltage 12.8 months 59% 29%
Théon et al, JAVMA, 1993 Megavoltage 12.6 months 60% 25%
Henry et al, JVIM, 1998 Megavoltage 14.1 months - -