The body usually sends out some signals to alert us in the pre-cancer stage, but not all symptoms in the early stage of cancer are typical, and the appearance of physical changes does not necessarily mean the occurrence of cancer. There are not as many as 18 signs as there are different sites of early stage cancer and the symptoms appear differently. Usually, if there is progressive weight loss without any cause, body lumps, unexplained fever, or sudden itching of the skin in people with non-allergic constitution, it may indicate the occurrence of cancer. In addition to the above manifestations, some cancers may also have some unique omens: 1. Prolonged mouth ulcers: Normal mouth ulcers can generally heal themselves in 1-2 weeks. If a long-lasting ulcer with hard bottom appears in the mouth and is not relieved by the application of medication for mouth ulcer, the occurrence of malignant changes in oral mucosa should be considered; 2. Irritating dry cough of unknown cause: Early lung cancer often manifests as irritating dry cough. If irritating dry cough occurs continuously without infection, sometimes coughing up blood, one should be alerted to the presence of lung tumor; 3. Persistent hoarseness: some malignant tumors near the throat, such as thyroid malignant tumor or laryngeal cancer, which compress the vocal cords or laryngeal nerve, may also cause hoarseness. So when there is unexplained hoarseness, attention should also be paid; 4. Changes in moles: If the moles on the body suddenly become large and irregular in shape, or if symptoms such as pus flow occur, it should be promptly checked whether it is melanoma; 5. Upper abdominal distension or difficulty in eating: upper gastrointestinal tumors and liver tumors usually do not have obvious symptoms in the early stage, but only show indigestion, and esophageal tumors may also be accompanied by difficulty in eating; 6. Change of stool: including change of stool habit, change of color and change of shape. Change in stool habit may indicate intestinal problems, and early intestinal tumor may also only show change in stool habit. Changes in stool color, such as tarry color, may indicate upper gastrointestinal tumor bleeding, and clay-like stool may indicate occupational lesions of the gallbladder or pancreas. The irregularity of stool or obvious scratches on the stool may be due to the occurrence of occupational lesions in the intestinal tract. 7, urine changes: when hematuria or difficulty in urination or incomplete urination occurs, malignant lesions of the urinary system should also be considered. 8, abnormal vaginal discharge: under normal circumstances, women’s vaginal discharge is transparent or light yellow, and the state is related to the menstrual cycle. If abnormalities such as foul-smelling purulent discharge or contact bleeding occurs, as well as non-menstrual bleeding, attention should be paid to the occurrence of gynecological malignant tumors. In addition, the omens of cancer development in different people and systems vary from person to person, and not the presence of the above symptoms means that cancer must occur. We should be more vigilant in our daily life and pay attention to health examination and cancer screening, so that even if there are diseases, they can be detected and treated early.