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Metastatic Tumors of the Lungs |  |
| A localized tumor may extend to the lungs by dissemination through hematogenous or lymphatic routes or by direct extension of tumor cells. Certain primary tumors, such as mammary adenocarcinoma, osteosarcoma, hemangiosarcoma, and oral melanoma, most commonly metastasize to the lungs. The lungs may be the only site of metastasis, or there may be concurrent metastasis in other organs; in the former, the diagnostic approach is to identify an occult primary tumor or to carefully review
the medical history for disclosure of previous tumor removal. Because pulmonary metastasis occurs late in the clinical course of a malignant tumor, prognosis is poor. |
| The signs of metastatic pulmonary disease are similar to those of primary lung tumors except that coughing is less common. Severity of signs depends on the anatomic location of the tumor and whether the lesions are solitary or multiple. |
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The diagnosis is similar to that for primary lung tumors. Because of the limitations of routine radiography, small lesions (≤3 mm in diameter), which are present in ≥40% of cases with pulmonary metastasis, may not be seen. |
| Radiography of the chest should precede removal of tumors with a known high incidence of metastatic spread to the lungs. The major goal of cancer therapy is prevention of metastasis rather than its eradication. Slow-growing or solitary metastatic lesions are best treated by surgical excision. Chemotherapy or radiation therapy may be useful with certain tumor types not amenable to surgical resection. Overall, the prognosis for animals with pulmonary metastasis is poor. |
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