Pancoast tumour is seen with cancer of -

Answer is 'a' i.e. Apical lobe of lung "Pancoast's (or superior sulcus tumor) syndrome results from local extension of a tumor growing in the apex of the lung with involvement of the eighth cervical and first and second thoracic nerves, with shoulder pain that characteristically radiates in the ulnar distribution of the arm, often with radiologic destruction of the first and second ribs." - Harrison