Pulmonary Metastases

Essentials of Diagnosis

• Identification of a primary cancer

• Radiographic findings consistent with pulmonary spread from the cancer (eg, nodules)

• Exclusion of other diseases in the differential diagnosis of multiple pulmonary nodules

General Considerations

• Represent metastases from extrapulmonary malignancies

• Almost any cancer can spread to the lung, usually hematogenously via the pulmonary artery

• Lung metastases are found in 20–55% of patients with various metastatic malignancies

Symptoms and Signs

• Symptoms are uncommon, but include cough, hemoptysis, and dyspnea in advanced cases

• Symptoms are most commonly referable to the primary tumor

Differential Diagnosis

• Bronchogenic carcinoma

• Lymphoproliferative cancer

• Tuberculosis

• Lung abscess

• Granulomas (eg, tuberculous, fungal)

• Coccidioidomycosis

• Histoplasmosis

• Sarcoidosis

• Silicosis

• Coal worker's pneumoconiosis

• Mycobacterium avium complex

• Arteriovenous malformations

• Rheumatoid nodules

• Hamartomas

• Granulomatosis with polyangiitis

• Methotrexate-induced

Laboratory Tests

• Appropriate studies should be ordered in a search for the primary tumor

• Occasionally, cytologic studies of pleural fluid or pleural biopsy are diagnostic

Imaging Studies

• Chest radiograph usually shows multiple spherical densities with sharp margins

• Lesions are usually bilateral, pleural, or subpleural and are more common in lower lung zones

• CT imaging of the chest, abdomen, and pelvis may reveal the site of a primary tumor and will help determine feasibility of surgical resection of the metastatic lung tumors

• PET-CT FDG scan is helpful in identifying the site of a primary cancer or identifying other areas of extrathoracic metastasis

• Mammography should be performed in a search for the primary tumor

Diagnostic Procedures

• If a primary tumor cannot be found, tissue from lung lesions may be obtained by bronchoscopy, percutaneous biopsy, or thoracotomy

Surgery

• Resection of a solitary pulmonary nodule is often prudent in a patient with known current or prior extrapulmonary cancer

• Local resection of one or more pulmonary metastases is feasible in a few carefully selected patients with various sarcomas and carcinomas (such as testis, colorectal, and kidney)

• Only about 15–25% of patients with metastatic solid tumor have metastases limited to the lungs and are therefore surgical candidates

• Surgical resection should be considered only if

  • The primary tumor is under control

  • The patient has adequate cardiopulmonary reserve to tolerate resection

  • All metastatic tumor can be resected

  • Effective nonsurgical approaches are not available

  • There is no evidence of extrathoracic metastases that are not controlled

• Patients who are not surgical candidates but have solitary or limited metastatic disease to the lungs may be candidates for stereotactic radiosurgery, radioablation or cryotherapy

• Repeat surgery for pulmonary metastases can be performed as long as the criteria for pulmonary metastatectomy are still met

Therapeutic Procedures

• Management consists of treatment of the primary malignancy and any pulmonary complications

Prognosis

• Overall 5-year survival rate of 36% and 10-year survival rate of 26% after complete resection of pulmonary metastases

When to Refer

• All patients deserve an evaluation by a multidisciplinary lung cancer evaluation and treatment program

• For bronchoscopy or thoracotomy

• All patients with advanced disease should be referred to a palliative care specialist

When to Admit

• Respiratory distress, altered mental status, pain control