A Pancoast tumor is a type of lung cancer that occurs at the top of the lung, near the shoulder. It is often associated with specific symptoms due to its location, such as shoulder pain, Horner's syndrome, and weakness in the hand. These tumors can invade nearby structures, including the ribs and nerves. Diagnosis typically involves imaging tests like CT scans or MRI to assess the tumor's size and spread. Treatment options may include surgery, radiation therapy, and chemotherapy, depending on the tumor's stage and the patient's overall health. Early detection is crucial for better outcomes.