If lung cancer metastasizes to the hilar lymph nodes, it may cause pneumonia and shortness of breath due to compression of the airway; if it metastasizes to the mediastinal lymph nodes, it may cause hoarseness due to compression of the recurrent laryngeal nerve and difficulty in breathing due to compression of the trachea; if it metastasizes to the supraclavicular or cervical lymph nodes, a hard, fused mass may be palpated under the skin of the neck, often without pain.