Lung metastases from various malignancies combined with primary lung cancer.

Various tumors metastasize to the lung, and they are often detected as multiple nodules. We report on two cases of such multiple lung metastases combined with primary lung cancer: a myxoid liposarcoma in the right thigh and a colon cancer. In each case, a pulmonary metastasectomy revealed that one of the tumors was primary lung cancer. Regardless of recent advances in computed tomography for detecting small pulmonary nodules and ground-glass opacity components, which indicate possible primary lung cancer, the preoperative differential diagnosis for either metastatic or primary lung cancers is usually difficult because they are too small to obtain enough tissue for diagnosis, except by surgery. When nodules are removed and diagnosed as lung metastasis combined with primary lung cancer, additional treatment should be considered depending on the prognosis of each disease.