What are the common salivary gland tumors? Ninety-five percent of salivary gland tumors are from glandular epithelium, while mesenchymal tissue tumors are mainly from vascular tissue, such as hemangioma and lymphadenoma. Epithelial tumors are subdivided into adenomas and carcinomas according to histopathology. Adenomas mainly include mixed tumors, myoepithelial tumors, adenolymphomas, basal cell adenomas, eosinophilic adenomas, ductal adenomas, sebaceous adenomas, ductal papillomas, cystic adenomas, etc. Among them, mixed tumors are the most common. Carcinomas include blast cell carcinoma, mucinous epidermis-like carcinoma, adenoid cystic carcinoma, pleomorphic low-grade malignant adenocarcinoma, epithelial myoepithelial carcinoma, salivary ductal carcinoma, adenocarcinoma, squamous carcinoma, malignant mixed tumor, basal cell adenocarcinoma, sebaceous gland carcinoma, eosinophilic adenocarcinoma, papillary cystic adenocarcinoma, mucinous adenocarcinoma, myoepithelial carcinoma, undifferentiated carcinoma and other carcinomas, the first three being the most common. Histopathologically, the tumors occurring in both large and small salivary glands are basically similar, but the proportion of different types of tumors varies. For example, adenoid cystic carcinoma occurs in far more small salivary glands than large salivary glands, and adenolymphoma and adenoid cell carcinoma occur in more than 90% of parotid glands. The proportion of benign and malignant glandular epithelial tumors in large and small salivary glands also differs. For example, benign tumors in parotid gland account for 2/3 of tumors, benign and malignant tumors in submandibular gland and small salivary gland each account for 1 in 2, while 90% of tumors in sublingual gland are malignant. What are the clinical characteristics of parotid tumors? Among parotid tumors, benign tumors account for about 2 out of 3 and malignant tumors account for 1 out of 3. 80% of parotid tumors occur in the superficial lobe of the parotid gland. The most common benign tumor is mixed tumor, followed by adenolymphoma; the most common malignant tumor is mucinous epidermis-like carcinoma, and most of them are highly differentiated type. Parotid tumors, whether benign or malignant, can occur at any age, but are most common between the ages of 30 and 50. Benign tumors are painless and slow growing, and are often discovered unintentionally. The duration of the disease varies from a few days to several years. Mixed tumors are usually centered on the earlobe and grow painlessly and gradually, spherical or oval, or nodular in shape. The surface is smooth, tough, non-adherent to the surrounding tissue, and mobile. Larger tumors may have a typical nodular appearance with an uneven surface and no adhesion to the skin, often soft at the elevated areas and hard at the low areas. Except for facial deformities, mixed tumors generally do not cause facial nerve dysfunction. If a mixed tumor grows slowly and exists for many years, and then grows faster in the near future and shows signs of malignancy such as pain, tumor no longer moving and facial nerve paralysis, malignancy should be considered. The malignancy rate of mixed tumors is about 5% to 10%. Adenolymphomas are common in men over 50 years of age, with a male to female ratio of 10 to 1. They are usually found in the lower posterior part of the parotid gland and are usually 3 to 6 cm in diameter, with a smooth, soft, sometimes wavering surface. Adenolymphoma is multifocal and can occur in one gland or in both glands at the same time, with a multifocal rate of about 15%. All other types of adenomas have clinical manifestations similar to mixed tumors. Malignant tumors of the parotid gland are fast-growing, and facial nerve palsy occurs in about 20% to 30% of cases, often with spontaneous pain. The mass is usually hard, can infiltrate surrounding tissues, is immobile, and often has pressure pain. Be careful not to mistake the mobility of the gland due to tumor infiltration for the mobility of the tumor. Hypodifferentiated adenocarcinoma, mucinous epidermis-like carcinoma, undifferentiated carcinoma and squamous carcinoma of the parotid gland have the above characteristics and have a higher chance of cervical lymph node metastasis. However, the most common type of malignant tumor in parotid gland, highly differentiated mucinous epidermis-like carcinoma, often does not have the above-mentioned typical malignant features and resembles benign tumor, and the tumor is usually hard. Highly differentiated mucinous epidermoid carcinoma and adenoid cystic carcinoma often directly invade the intra- or periglandular lymph nodes. Deep lobe tumors of the parotid gland are not easily detected at an early stage due to their concealed location. During physical examination, a mass can be found above the posterior tonsils and the soft palate, or the posterior mandibular concavity can be plumped up and an inactive mass can be found, which can be pushed during double-handed examination. Malignant tumors in the deep lobe are often associated with restricted mouth opening, headache, hearing loss, tinnitus, facial paralysis, etc. The typical location of parotid paraglandular tumor is 1 cm from the lower border of the zygomatic arch and zygomatic body, which is often misdiagnosed as a buccal tumor. What are the principles of surgery for parotid tumors? Surgery is the only effective means of treating parotid tumors, 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, as this may lead to recurrence of tumor cell implantation. The standard surgical procedure for benign parotid tumors is to preserve 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. Before surgery, 1% methylene blue staining can be injected from the parotid duct to make the gland light blue and the nerve silvery white, which is easily recognizable. Tumor enucleation with parietal peeling is absolutely contraindicated during surgery. Mixed tumors have different thicknesses of envelope and are often incomplete, and there are often tumor cells invading inside the envelope. 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 by simply peeling along the tumor envelope. The surgery of parotid malignant tumor should follow the surgical principles of malignant tumor, the tumor should be removed within the normal tissue, all the lobes of the gland should be removed, and the facial nerve should be sacrificed if there is facial nerve paralysis or if the facial nerve passes through the tumor during surgery, and then the nerve graft should be considered. If the facial nerve is adjacent to the tumor but can be separated and there is no clinical sign of facial nerve palsy (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, and the lymph nodes in the parotid gland and around the gland near the tumor should be removed together with the surgery. For most of parotid cancer, only therapeutic cervical lymphatic dissection can be performed. What are the clinical features of submandibular gland tumors? Benign and malignant tumors of the submandibular gland account for about 1 in 2. All benign tumors are mixed tumors; among malignant tumors, adenoid cystic carcinoma is the most common, followed by mucinous epidermis-like carcinoma. The clinical manifestation of submandibular gland tumors, no matter benign or malignant, is the appearance of masses in the submandibular triangle. Benign mixed tumors show painless slow growth with clear circumference and movable masses that are round or can be typically nodular in shape. Malignant tumors are generally faster growing, but there are cases with a history of several years where the mass is hard and often has spontaneous pain or tenderness and symptoms of nerve involvement. If the lingual nerve is involved, tongue pain or tongue numbness may occur, most obvious at the tip of the tongue; if the lingual nerve is involved, tongue paralysis may occur, i.e. tongue movement is limited, and the tip of the tongue is distorted to the affected side when extending the tongue. Adenoid cystic carcinoma of submandibular gland is asymptomatic in early stage and resembles benign tumor. It has a long course and grows slowly. The swelling is of different sizes, flat and round or slightly nodular in shape, with a hard texture. Adenoid cystic carcinoma is relatively mobile at the beginning, but often infiltrates surrounding tissues, resulting in restricted activity. Adenoid cystic carcinoma is especially prone to infiltrate nerves and expand along nerve fiber bundles, resulting in pain and other symptoms. Mucinous epidermoid carcinoma is usually well circumscribed and may be solid or cystic, and spontaneous ulceration may result in the flow of light tan, mucous fluid. Regional lymph node metastasis can occur in adenocarcinoma and low-differentiated mucous epidermis-like carcinoma. The lymph nodes around the submandibular gland are often invaded by malignant tumors. Removing the submandibular gland together with the tumor or performing submandibular triangle debulking is the best treatment for submandibular gland tumor. What are the clinical features of sublingual gland tumor? Sublingual gland tumors are rare, 90% of which are malignant, mainly adenoid cystic carcinoma and mucinous epidermis-like carcinoma. Since the sublingual gland is located at the bottom of the mouth, it is not easy for patients to detect the tumor after it occurs, but many patients find it when the sublingual mass prevents the denture from being put in or during routine oral examination. In such cases, the sublingual area should be carefully palpated with both hands, and the mass can often be palpated. If the lump involves the sublingual nerve, tongue movement disorders, slurred speech, and tongue tip deviation to the affected side when extending the tongue may occur. When the mass in the sublingual gland is small, it should be distinguished from a submandibular duct stone. Treatment is mainly surgical resection, and other treatment is the same as parotid tumor. What are the clinical characteristics of small salivary gland tumor? The minor salivary glands are located in the submucosa, and the palate gland is the most abundant, so 70% of minor salivary gland tumors occur in the posterior palate. Among small salivary gland tumors, benign mixed tumors are most common, while malignant adenoid cystic carcinoma and mucinous epidermis-like carcinoma are common. Small salivary gland tumors often appear as slow-growing masses, but have different characteristics in different sites. Palatal gland tumors are commonly found at the junction of the hard and soft palate on one side and are less mobile. Benign tumors can produce compressive resorption of palatal and alveolar bone. Malignant tumors can destroy the bone, and when the alveolar bone is involved, toothache and tooth loosening can occur. Upward along the palatine major nerve can involve the infraorbital nerve, causing symptoms such as numbness and discomfort in the palate, numbness in the infraorbital area and upper lip on the affected side. If the tumor grows up, it can fill up the whole mouth and cause dysfunction of opening and closing the mouth and eating. Posterior mandibular molar gland tumor mainly manifests as gingival swelling and tooth loosening, which is easily misdiagnosed clinically as mandibular tooth pericoronitis, and may be misdiagnosed again as dry socket or marginal osteomyelitis when the incision does not heal after tooth extraction due to misdiagnosis. Therefore, when gingival swelling in the posterior region of the molar is found to be different from general pericoronitis, high vigilance should be exercised and tissue should be excised for pathological examination during tooth extraction. Tumors in this area are most commonly highly differentiated mucous epidermis-like carcinoma. Tumors of the tongue gland are most common in the root of the tongue, and their main symptoms are pain at the root of the tongue, foreign body sensation, and affecting swallowing. Malignant tumors of tongue root are common, and the common ones are adenoid cystic carcinoma and mucous epidermis-like carcinoma, which are prone to lymphatic metastasis due to rich lymphatic circulation in tongue root. Tumors of the lip and cheek are clearly defined active masses, mostly in the upper lip. The treatment of small salivary gland tumors mainly adopts surgical excision, and other treatment principles are the same as parotid tumors.