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

Clinical Features

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

•hypercalcemia of malignancy has been reported in cats and dogs

•endogenous lipid (cholesterol) pneumonia associated with bronchogenic carcinoma in 1 cat

Diagnosis

Thoracic Radiographs

•lung tumors have a variable radiographic appearance in cats, with 3 main presentations:

•mixed bronchoalveolar pattern (33%)

•ill-defined alveolar mass (22%)

•pulmonary mass with cavitation (56%)

•furthermore, bronchial disease is common in cats with primary lung tumors

•caudal lung lobes are most commonly affected

•diffuse lesions are present in 24%-53% cats

•uncommon findings: multiple or miliary lesions, hilar lymphadenopathy, and pleural effusion

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)

Clinical Staging

Treatment

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

Chemotherapy

•systemic chemotherapy may offer some benefit

•intracavitary chemotherapy ± sclerosing agents (i.e., talc or tetracycline) have been used for malignant effusions

Prognosis

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