Coughing up blood (hemoptysis) after two chemotherapy treatments for stage 3a lung squamous cancer may be caused by tumor invasion of peripheral blood vessels, drug side effects and other factors. 1. Tumor infringes on peripheral blood vessels: if tumor cells of squamous lung cancer infringe on capillaries after chemotherapy, symptoms such as blood in sputum and frothy bloody sputum may occur. If it violates large bronchial arteries, it may lead to coughing up fresh blood and massive hemoptysis. 2. Drug side effects: chemotherapeutic drugs such as cisplatin, gemcitabine, vincristine and so on generally have the effect of inhibiting bone marrow, which may lead to the reduction of white blood cells and platelets, thus resulting in the phenomenon of spontaneous hemorrhage, which is manifested as hemoptysis. If hemoptysis occurs after two chemotherapy treatments for stage 3A squamous lung cancer, one should go to the hospital in time to clarify the cause of the disease with the help of professional doctors and then take targeted treatment.