Oral cancer refers to all malignant tumors in the oral structure, and more than 90% are squamous epithelial cell carcinomas that occur in the cells of the oral mucosa. In general, the oral cavity includes the lips, the buccal mucosa (the lining of the lips and cheeks), the teeth, the floor of the mouth beneath the tongue, the first two-thirds of the tongue, the front part of the roof of the mouth (hard jaw), the gums, and the small area behind the molars. Oral cancer is one of the more common malignant tumors of the head and neck and tends to occur in areas that are more mobile or easily irritated. According to statistics, it most often occurs in the tongue, followed by the floor of the mouth and the buccal mucosa in China. Pre-cancerous lesions are not oral cancer, but they are oral mucosal lesions with high malignant potential. According to research, if the source of irritation exists for a long time or is ignored, the chance of malignant transformation can be as high as 10% or more. Therefore, the appearance of abnormal colored plaques in the mouth is a major clue that the body is telling us that we need to seek medical examination. Pre-cancerous lesions of the oral cavity include leukoplakia, erythroplakia and lichen planus, for example, erythroplakia, in which the oral mucosa is originally pink, but it appears as a blood red. Symptoms ulcers and discoloration of oral mucosa should be alerted 1. Changes in the color or appearance shape of oral mucosa, such as turning white, red, or dark, or the pre-existing mole increases in size, surface height, hardens in texture and appears as an ulcer. 2. Unexplained lumps in the mouth or any part of the neck or oral mucosal ulcers that have not healed for more than two weeks. According to the growth pattern of cancer, there are two main types of ulcers and cauliflower type. Generally speaking, normal people with poor oral immunity often have oral ulcers, but they usually heal within a week, and the location of the ulcer is wandering, such as sometimes it grows in this place and sometimes in that place. However, if the ulcer does not heal after a month, it may be cancerous or tuberculosis, and it is necessary to go to the hospital for some tuberculosis-related tests. If tuberculosis ulcer is ruled out, then it is basically a cancerous ulcer. 3.According to the location of the tumor, the patient will show the corresponding focal symptoms. If it grows in the buccal muscle, it may show that the mouth cannot be opened; if it invades the tongue, it will show the symptoms of movement disorder, loss of consciousness or numbness on the half side of the tongue. 4.If there is metastasis, the metastatic area will also have corresponding manifestations. Oral cancer is easy to metastasize to the nearby lymph nodes in the neck, sometimes the primary lesion is very small and even the symptoms are not obvious, but the lymph nodes in the neck have already metastasized. Therefore, if the lymph nodes in the neck are suddenly enlarged, the oral cavity should be examined. Then there is distant metastasis such as bone metastasis, which will show pain. Tip: Most oral cancer patients are already in the middle and late stage when they come to the hospital. The key to early detection of oral cancer is self-identification of “precancerous lesions”, especially its “high-risk phase”, and the characteristics of “early stage cancer”.