Nasopharyngeal cancer is very painful in the late stage, mainly in the following ways: 1. When the cancer invades the cranium, it can lead to persistent headache, which cannot be relieved by medication. When nasopharyngeal cancer invades the internal and external pterygoid muscles, patients may have difficulty in opening their mouths and cannot open their mouths to eat. 2. When nasopharyngeal cancer invades the cranial nerves, such as the trigeminal nerve, patients may experience facial numbness, and invasion of the optic nerve may lead to diplopia, loss of vision and inability to see. 3. When nasopharyngeal cancer invades the lymph nodes in the neck, the lymph nodes will be enlarged and the lymph nodes will compress the large arteries and blood vessels in the neck, which may lead to fainting, hoarseness, difficulty in breathing, asphyxia, etc. 5. When nasopharyngeal carcinoma invades skin and muscle, it can lead to skin and muscle-related diseases.