When Patient and Clinician Miss the Signal: A Delayed Diagnosis of Pancoast Tumor.

Pancoast tumors, located at the pulmonary apex, present a diagnostic challenge due to their atypical clinical presentation, often mimicking benign musculoskeletal conditions of the shoulder. We report the case of a 49-year-old man with a history of chronic tobacco use who presented with persistent right shoulder pain, initially attributed to rotator cuff tendinopathy based on suggestive ultrasonographic findings. Despite symptom progression and nocturnal pain refractory to conventional therapy, no early thoracic imaging was pursued. A previously performed shoulder radiograph showed apical pleural thickening that went unrecognized by a non-specialist, missing an early sign of malignancy. Diagnostic delay was further compounded by the patient's reluctance to undergo chest imaging, fueled by fear of a cancer diagnosis and the psychological burden associated with long-term smoking. The diagnosis of apical bronchogenic adenocarcinoma was delayed until an advanced stage, precluding curative treatment. The patient died 12 days after diagnosis from cachexia and sepsis. This case highlights the need for the early consideration of apical lung tumors in patients with atypical shoulder pain, particularly among smokers. The careful interpretation of initial imaging and the awareness of psychological barriers to diagnosis are critical to improving outcomes.