Oral cancer usually has the characteristics of rapid progress, extensive infiltration and poor prognosis, and more than half of the patients who first consult the doctor are already at advanced stage. However, oral cancer is not formed suddenly, if we can grasp the warning signals shown in early stage to achieve early diagnosis and early treatment, the cure rate can be improved. Usually, most patients with oral cancer will have 4 signs: ulcers, lumps, discoloration and pain. If you find the following signs, you should be especially vigilant and seek medical treatment as early as possible.1. Ulcers: Most of the ulcers on the tongue, lips, gums and cheeks inside the mouth are inflammatory, but a few of them are indeed cancer ulcers. Chronic inflammatory ulcers that do not heal are prone to cancer if they are often stimulated by chewing and talking; 2. Lumps: No matter how small they are at the beginning, they should be taken seriously if they are increasing in size, ectropion or rapidly increasing. Inflammatory lumps are characterized by good and bad, swollen and subsiding, while cancerous lumps will only increase and will not subside; 3.Colored spots: white and red spots. If the white spots have rough surface, hard nodes, infiltration, protrusion, or granular granules on the surface, this is a typical precancerous state and must be paid great attention to; 4. Pain: After suffering from oral cancer, patients are prone to painful symptoms, such as posterior maxillary cancer, when it invades the guanxi muscle, it can show pain or be accompanied with mouth opening restriction, etc. In addition, besides the above 4 signs, some patients may also show signs such as facial palsy and lower lip numbness. For example, cancer in parotid gland may easily destroy facial nerve and cause facial palsy with distorted mouth and eyes, while mandibular cancer may show early symptoms such as numbness of one side of lower lip due to the involvement of lower alveolar nerve that travels in the mandible.