Metastatic tumors to the lung are extremely common. In fact, the lung ranks number one in terms of organs harboring metastatic diseases. Lung involvement in some autopsy series cite pulmonary involvement in up to 54% of the cases. Factors accounting for the high number of metastasis to the lungs include their rich capillary network and possibly a favorable “seed and soil” disposition inherent to pulmonary tissues. In relative order of frequency, metastatic tumors to the lung originate from carcinomas in the breast, colon, stomach, pancreas, kidney, prostate, liver, thyroid, adrenal, male genital tract, and the female genital tract. Sarcomas from bone, soft tissue, and visceral sites are prone to disseminate via the blood stream and frequently metastasize to the lungs. Melanomas also spread to lungs but not frequently. Rarely, a primary lung tumor will spread to involve both lungs closely mimicking metastatic disease. Despite extensive work up, some metastatic carcinomas can not be classified in regards to their site of origin.