In the early stages of lung cancer, it generally does not cause shoulder pain. Early-stage lung cancer often does not involve critical structures and typically does not produce noticeable clinical symptoms. However, a small number of central lung cancers may cause symptoms related to coughing. Moreover, shoulder pain can occur in cases of lung cancer, often seen in superior sulcus tumors. A superior sulcus tumor, also known as a Pancoast tumor, is a tumor located at the top of the lung. As the tumor grows, it may compress the brachial plexus nerves, leading to symptoms such as shoulder pain and throat pain. It can also cause symptoms like enophthalmos (sunken eyeball) and pupil constriction. Therefore, when encountering these signs clinically, it is necessary to consider the possibility of a superior sulcus tumor and conduct examinations like a chest CT scan for evaluation.