1.Imaging examination (1) X-ray examination: to understand the bone tissue tumor and the scope of invasion. For example: odontogenic cyst, benign and malignant tumor of jaw bone, etc., often photographed with curved spreading film, maxillary wah position, mandibular front and side position, maxillary occlusion film, etc. For malignant tumors, chest radiographs are routinely taken to check for lung metastases. The nature of parotid tumor can be understood by parotid gland angiography. (2) CT examination: (3) MRI examination: It is suitable for the diagnosis of carotid body tumor, tongue root tumor, salivary gland tumor and lymph node metastasis. (4) Ultrasonography: Principle: When ultrasound propagates in human tissues, there are different echograms due to different density and characteristics of various tissues. For soft tissue tumor, it can determine whether it is substantial or cystic, and accurately indicate the size of tumor. In addition, according to the clarity of the circumference and the uniformity or not of the distribution of light spots within the tumor provides a judgment whether the tumor is benign or malignant. (5) Radionuclide examination (isotope examination): Since there is a difference in metabolism between tumor cells and normal cells, the distribution of nuclei will be different. After administering or injecting radionuclides to patients, scanning can be applied to determine the distribution of radioactive substances for the next diagnosis and differential diagnosis. To diagnose malignant tumor of jaw bone, 99mTc is mainly used; 131 iodine is available for ectopic thyroid gland in oral and peri-mandibular area; it is important to check tumor of salivary gland (adenolymphoma) and metastasis of bone in whole body. (6) Genetic diagnosis: The occurrence of tumor is the result of the accumulation of genetic changes in cells, including: ① activation and overexpression of oncogenes. ② Mutation and loss of oncogenes. ③ Microsatellite instability, with abnormal tandem repeats of nucleotides distributed in the genome. ④Mismatch repair gene mutation, resulting in cytogenetic instability or tumorigenic susceptibility. 2.Puncture examination Cystic masses can be diagnosed based on the color and trait of the puncture fluid, such as jaw cyst, gill slit cyst, sublingual gland cyst and choroidal tumor. For salivary gland or some deep tumors, the diagnosis of benign and malignant tumors can be as high as 95% by puncture smear, cytological examination or “fine needle aspiration biopsy”. (3) Biopsy (1) Clamp is suitable for tumor with superficial location or ulcer (2) Excision is performed under blocking anesthesia (3) Aspiration biopsy is suitable for large tumor with intact surface of deep tumor and enlarged lymph nodes in the neck. (4) Excisional biopsy is applicable to small tumors or lymph nodes, and the whole piece is excised and sent for examination (5) Frozen biopsy is applicable to intraoperative, and the diagnostic rate reaches 95%↑. 4.Tumor marker examination Some special chemical substances are found in the blood, urine or other body fluids of malignant tumor patients, which usually appear in the form of carcinoembryonic antigen (CEA), hormones, receptors, various oncogenes and enzyme proteins, and are mainly produced, secreted and released by tumor cells, so the laboratory tests based on blood and urine assist in diagnosis. It also provides monitoring of the treatment effect and prognosis.