Diagnosis and differential diagnosis: 1. The most common sites of parotid tumors: 1. A painless mass below the ear on the side of the face. The most common cause of a parotid mass above the front of the ear screen is an enlarged parotid lymph node. In elderly patients, especially those with a history of skin cancer, the possibility of metastatic cancer must be considered for this mass. If a definite mass in the parotid gland is found, whether it is a tumor should be excluded from mumps, purulent parotitis, parotid tuberculosis, parotid duct stones and bilateral diffuse parotid enlargement. What are the types of benign tumors of parotid gland? Polymorphic adenoma (mixed tumor “benign mixed tumor” name has been abandoned because this lesion has local recurrence and is considered as localized type of cancer) 75%, adenolymphoma 5-10% eosinophilic adenoma; large eosinophilic granuloma; benign lymphoepithelial lesion; hemangioma and cyst in parotid area, etc. What are the types of malignant tumors of parotid gland? Mucosal epidermoid carcinoma (about 1/3); malignant mixed tumor; glandular blastoma; adenocarcinoma; adenoid cystic carcinoma; epidermoid carcinoma. Differential diagnosis of parotid tumors Differentiation of benign and malignant tumors of parotid gland: 1. Benign tumors of parotid gland: The most common one is mixed tumor; it is a “borderline tumor”, which has the possibility of recurrence and malignancy after surgery. When examining the tumor, the boundary is generally clear and the texture is hard. The surface of the mass is not smooth, mostly nodular, without facial palsy, which may occur if malignant. Adenolymphoma, also known as papillary lymphocystic adenoma, is next. They are small in size (within 4cm in diameter), well-defined, soft and mobile, and do not adhere to the surrounding tissues. Malignant tumors of the parotid gland: there are many types, the most common being mucinous epidermoid carcinoma, which accounts for about 1/3, and the rest are adenocarcinoma, glandular follicular cell carcinoma, pleomorphic low grade malignant adenocarcinoma, adenoid cystic carcinoma and malignant mixed tumors in that order. Both of them present as painless preauricular masses. The main differentiation points of benign tumors: benign tumors are round-like, with regular, clear and smooth edges and clear demarcation with surrounding structures. The main differentiating points for malignant tumors are: (1) the mass has unclear boundaries and is diffusely invasive; (2) the center of the tumor is necrotic, showing hypodense areas or uneven density; (3) the shape of the tumor is irregular and lobulated; (4) it is accompanied by enlarged lymph nodes in the neck. Treatment Surgical operation is the only effective means to treat parotid tumor, and whether the first operation is correct and thorough is the key to cure. Two principles must be followed in surgery for benign parotid tumors: one is to ensure that the facial nerve is not damaged, especially the temporal facial trunk; the other is to avoid breaking the tumor envelope, otherwise it will lead to recurrence of tumor cell implantation. The standard procedure for benign parotid tumors is to save the facial nerve and remove the lobe and tumor together. Due to the irregular shape of the parotid gland with multiple protrusions, it is not possible to remove all of the lobe tissue. Therefore, the extent of resection is often determined by the location of the tumor within the gland and the intraoperative situation. Tumor enucleation with parietal peeling is absolutely contraindicated during surgery. The thickness of the peritoneum of mixed tumors varies and is often incomplete, and there are often tumor cells invading inside the peritoneum. Removal of mixed tumors by paracentesis may lead to tumor recurrence. Adenolymphoma itself is multifocal in nature and its occurrence is closely related to lymph nodes. In addition, some malignant tumors of the parotid gland are clinically similar to benign ones, and it is not allowed to remove the tumor simply by peeling along the tumor envelope. Some benign tumors, such as parotid cysts and hemangiomas, can be removed by simple tumor resection. Surgery for malignant tumors of the parotid gland should follow the principles of surgery for malignant tumors and completely remove the tumor within the normal tissues, and all the lobes of the gland and the facial nerve should be removed. If the facial nerve is adjacent to the mass but can be separated, and there are no clinical signs of facial nerve paralysis (except for adenoid cystic carcinoma and highly malignant tumors), the facial nerve can be preserved, but radiation therapy should be performed after surgery. For squamous carcinoma, undifferentiated carcinoma, low differentiated adenocarcinoma, mucinous epidermis-like carcinoma and papillary cystic carcinoma, selective cervical lymphatic dissection should be performed; for highly differentiated mucinous epidermis-like carcinoma and adenoid cystic carcinoma, they can directly invade the lymph nodes, so the lymph nodes in the parotid gland and around the gland near the tumor should be removed together with the surgery. For squamous carcinoma, undifferentiated carcinoma, adenocarcinoma, low-differentiated mucinous epidermis-like carcinoma and papillary cystic carcinoma, postoperative radiation therapy is recommended. If the surgery is incomplete due to the preservation of important tissues, or if the pathological examination of the postoperative mass is positive, postoperative radiotherapy is necessary. Postoperative radiotherapy should be given no later than 6 weeks after surgery. There is no systematic and standardized treatment plan for the chemotherapy of salivary gland cancer. Commonly used drugs include cisplatin, methotrexate, 5-FU, adriamycin, etc. If malignant tumor does not invade the facial nerve, it should be preserved. If malignant tumor involves the facial nerve, under the principle of complete removal of the tumor, the main trunk of the facial nerve and the temporal facial trunk should be preserved according to the situation in order to maintain the function of eye closure, and if necessary, all of them should be removed together with the tumor. If the facial nerve is tightly adhered to the tumor or penetrates between the tumor, it is not easy to separate the nerve during surgery. There are five ways to find the facial nerve during parotid tumor surgery, among which the most cases are to find the common trunk of facial nerve and buccal branch of facial nerve, followed by cervical branch, mandibular margin branch and temporal branch. If the tumor is located in the caudal lobe, then the buccal branch or the mandibular rim branch will be searched first instead of the common facial nerve trunk; if the tumor is located on the gland, then the mandibular rim branch can be searched first; if the tumor is located in the front of the parotid gland, then the common facial nerve trunk can be considered to be searched first.