The common symptoms of lung cancer are cough, hemoptysis, chest pain and fever, but there are a few patients, especially those with tumors located in the upper lobes of both lungs, who have shoulder pain as their first symptom. Such patients are easy to be misdiagnosed. Wang, a 51-year-old male patient, developed intermittent vague pain in the right shoulder and back in April 2003 without any obvious cause, and was treated as periarthritis in the local hospital without any significant improvement. In December of that year, he developed right-sided chest pain accompanied by mild cough and sputum, and in January 2004, he was diagnosed with right upper lung cancer by chest CT. It is reported that among the lung cancer patients he has seen in the past two years, there are more than a dozen patients who have a history of misdiagnosis of frozen shoulder. He reminded people that if they have symptoms of periarthritis joint pain, especially in middle-aged and elderly people, they should think about the presence of other diseases in addition to periarthritis. This is done by taking a front and side chest x-ray when the patient is given an x-ray of the shoulder joint. If suspicious conditions are found, further chest CT examinations can be performed to rule out the possibility of lung cancer and avoid possible misdiagnosis and misdiagnosis