+ General Considerations

  • Primary lung tumors are rare in cats and account for < 1% of all tumors
  • Mean age 11-12 years
  • No breed predilection
  • Sex predisposition: females
  • Retroviruses may be involved in the pathogenesis of lung tumors in cats

+ Types of Lung Tumors

  • Carcinomas are the most common primary lung tumor in cats
  • Carcinomas are subclassified according to their location (i.e., bronchial, bronchoalveolar, and alveolar)
  • Bronchial carcinomas are more common (76%) than either bronchoalveolar or alveolar carcinomas
  • Bronchial ADC is the most common lung tumor in cats (66%-71%)
  • Bronchoalveolar ADC, anaplastic carcinoma, and SCC account for 10%-15% of lung tumors
  • 8% of primary pulmonary carcinomas are grade I, 23% grade II, and 69% of carcinomas are grade III

+ Metastasis

  • 75% metastatic rate for primary lung tumors in cats
  • Regional lymph node involvement in 29%-35% and distant metastasis in 46%-58%
  • Distant metastatic sites include pleural cavity in 65% and extrathoracic sites in 35%
  • Metastasis to multiple digits presenting as swelling of ≥ 1 toes and lameness without respiratory signs is a common primary complaint
  • Weight-bearing digits and 3rd phalanx are most commonly affected
  • Amputation is not palliative due development of further digit lesions and progressive non-respiratory disease

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+ Clinical Signs

  • Non-productive coughing, exercise intolerance, and other respiratory signs (i.e., dyspnea and tachypnea)
  • Systemic signs include lethargy and weight loss
  • Peracute presentation for hemothorax, pneumothorax, or malignant pleural effusion is uncommon

+ Paraneoplastic Syndromes

  • Hypertrophic osteopathy has been reported in cats and dogs
  • Paraneoplastic leukocytosis (which resolved following lung lobectomy) has been reported in 1 dog
  • Hypercalcemia of malignancy has been reported in cats and dog


+ Thoracic Radiographs

  • Lung tumors appear as a well-demarcated and spherical solitary ± cavitary mass in dogs
  • Caudal lung lobes are most commonly affected
  • Multiple masses may be present in dogs with primary pulmonary LSA, malignant histiocytosis, and lymphomatoid granulomatosis
  • Diffuse lesions are present in up to 37% dogs with primary lung tumors
  • Uncommon findings: multiple or miliary lesions, hilar lymphadenopathy, and pleural effusion

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+ Advanced Imaging

  • CT and MRI provide more accurate information on staging for resectability and detection of occult metastasis and hilar lymph node enlargement

+ Bronchoscopy

  • Indications: brush cytology of centrally located lesions extending into the bronchus
  • Trans-tracheal wash and bronchoalveolar lavage can be performed but are usually only diagnostic in diffuse LSA

+ Other Diagnostic Tests

  • Thoracocentesis if pleural effusion
  • Trans-thoracic FNA for larger lesions with a peripheral location, but larger tumors often have a necrotic centre resulting in a false-negative result
  • Trans-thoracic FNA has an 80% accuracy rate, but is associated with 12% mortality rate in cats and dogs
  • However, cytologic or histopathologic diagnosis is usually not required as results will not change treatment options (i.e., lung lobectomy)


+ Surgical Management

  • Lateral thoracotomy (4th-6th intercostal) for small to medium-sized lung tumors and hilar lymph node biopsy
  • Median sternotomy for large tumors and inspection of other lung lobes, but lymph node biopsy is more difficult
  • Lymph node aspirate or biopsy is recommended as neoplastic infiltration may not be clinically apparent
  • Partial lobectomy can be performed for peripheral tumors, but complete lung lobectomy preferred
  • Lobectomy can be performed with either stapling equipment or individual ligatures

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+ Chemotherapy

  • Systemic chemotherapy may offer some benefit
  • Intracavitary chemotherapy ± sclerosing agents (i.e., talc or tetracycline) have been used for malignant effusions
  • Inhalant chemotherapy using paclitaxel or doxorubicin has been investigated in dogs with primary and metastatic lung tumors:
  • Responses in sarcomas but not carcinomas to doxorubicin
  • Responses in both sarcomas and carcinomas with paclitaxel
  • Response rate 27% (6/22) with 22.5% PR (5/22) and 4.5% CR (1/22)
  • Intermittent and non-productive cough for 1-10 days in 50% dogs following inhalant doxorubicin
  • Allergic reactions common following paclitaxel administration


+ General Considerations

MST 115 days for cats with death or euthanasia due to metastatic disease

+ Clinical Stage or Lymph Node Involvement

  • Cats with lymph node metastases or distant metastatic disease have a significantly worse survival time:
  • MST for tumors without lymph node involvement: 412 days
  • MST for tumors with lymph node involvement: 73 days
  • MST for cats with metastatic lesions in digits: 67 days

+ Tumor Grade

  • Degree of tumor differentiation only prognostic factor in cats
  • 8% of primary pulmonary carcinomas are grade I, 23% grade II, and 69% of carcinomas are grade III
  • Cats with well-differentiated tumors have a better prognosis than undifferentiated carcinomas
  • MST for well-differentiated carcinoma: 23 months
  • MST for undifferentiated carcinoma: 2.5 months



T0No evidence of neoplasia
T1Solitary lung tumor surrounded by lung or visceral pleura - Primary Tumor
T2Multiple lung tumors of various sizes
T3Lung tumor invading adjacent tissue
N0No evidence of lymph node involvement
N1Bronchial lymph node involvement - Node
M0No evidence of metastasis
M1Evidence of distant metastasis with site specified - Metastasis
N2Distant lymph node involvement