Pancoast tumor accounts for 3%-5% of all non-small cell lung carcinomas. This tumor has a distinct clinical presentation through local invasion and the resulting clinical entity called Pancoast syndrome. This syndrome includes severe shoulder pain, arm pain, and Horner’s syndrome andatrophy of forearm and hand muscles. The differential diagnosis of arm and shoulder pain is extensive. Thoracic outlet syndrome and cervical disk disease are commonly mistaken for the Pancoast syndrome in the early clinical course. Diagnosis of Pancoast tumor is often late, and misdiagnosis is a common problem that can affect the prognosis. Therefore, Pancoast tumor should always be considered in differential diagnosis of radicular pain of the upper extremity.

We report a case of 55-year-old man who was admitted with right side severe pain in the back of the neck, shoulder and arm with numbness and tingling sensation in the medial aspect of the forearm and 4^th and 5^th fingers. These symptoms had initiated from 17 months ago, and the patient was treated for cervical discopathy and frozen shoulder.