 We want to examine the accuracy of needle biopsy in patients who had core samples taken from a lung mass in addition to, or in place of, fine needle aspiration. In this study we will focus on such patients who had no evidence of cancer according to the biopsy, to determine how many actually had a cancer that was missed by the biopsy. To accomplish this goal, we will need to review the medical records of these patients for one of two things: either a definitive diagnosis of the lung mass by some other means for example, surgical biopsy, or by seeing how the patient does over a period of time usually in conjunction with medical imaging tests such as chest x-rays or chest CT scans. To establish that a lung mass is benign by observing a patient over time, it is necessary to show that the lung mass disappears, becomes smaller, or remains unchanged in size for 2 years. 