Pancoast tumour presenting as shoulder pain with Horner's syndrome.

A 54-year-old man presented to the emergency department with a 4-week history of right shoulder pain radiating down his arm, with some associated sensory loss. Further questioning and examination in the department revealed a classical Horner's syndrome; miosis, partial ptosis and hemifacial anhidrosis. An initial chest X-ray was deemed to be unremarkable; however, further review by a radiologist noted asymmetrical right apical thickening. A subsequent high-resolution CT scan of the chest revealed a right-sided Pancoast tumour. This case highlights the importance of a thorough history and examination in identifying a rare cause of shoulder and/or back pain.