Salivary gland

There are numerous different types of salivary gland tumours, with the World Health Organization (WHO) regularly updating the corresponding classification. Tumours can be divided into benign and malignant (salivary gland cancer) and can occur in the major salivary glands (parotid gland, submandibular gland, sublingual gland) or in the accessory salivary glands beneath the mucosa of the upper respiratory and digestive tracts (e.g., in the oral cavity). In general, the risk of a malignant tumour is higher the smaller the gland is – in other words, a nodule in the parotid gland is less likely to be malignant than in the accessory salivary glands of the oral cavity. The most common benign salivary gland tumour is the pleomorphic adenoma, which usually must be removed due to the risk of malignant transformation. The most common malignant disease of the salivary glands is a metastasis of a cutaneous squamous cell carcinoma to the parotid gland, even though this is not a primary salivary gland cancer. The most common primary salivary gland cancer is the mucoepidermoid carcinoma.

An ultrasound-guided fine needle aspiration biopsy (FNA) is a diagnostic method that allows cells to be extracted from a salivary gland tumour in a minimally invasive and low-impact way. The procedure takes only a few minutes. During this process, the tumour is punctured with a fine needle under ultrasound guidance, and the cells obtained are sent to a cytology laboratory, where they are analysed according to standardized criteria. The results can be discussed with the patient after just a few working days. FNA is not only used for salivary gland tumours but also in other areas, such as thyroid nodules or abnormal lymph nodes. The risks of FNA are very low: mild pain or a small hematoma (bruise) may occur rarely; infections are very uncommon.

Facial nerve monitoring is a method of intraoperative neuromonitoring used to monitor the facial nerve during surgery. It is primarily used in parotid gland surgery (parotidectomy) but is also applied in surgery of the submandibular gland (submandibulectomy) and neck dissections. Electrodes in the muscles of mimic expression allow the facial nerve to be continuously monitored by measuring nerve signals or muscle potentials, thereby assessing its integrity. This makes the procedure safer and significantly reduces the risk of facial nerve weakness.

As with all surgical procedures, general complications such as bleeding/bruising, wound infections, impaired wound healing, or an unsightly scar can also occur in salivary gland surgery. In a parotidectomy, i.e., the (partial) removal of the parotid gland, there is an additional risk of weakness of the facial nerve, which runs through the gland. If the parotidectomy is standardized, performed routinely, and with the use of intraoperative neuromonitoring (facial nerve monitoring), this risk can be kept very low. If weakness does occur and the nerve remains intact, recovery fortunately occurs in almost all cases within 3 months. No nerve recovery occurs if nerve branches must be sacrificed during the removal of salivary gland cancer. However, various reconstructive procedures are available for this. Furthermore, after a parotidectomy, numbness of the skin of the cheek often occurs, which in the area of the earlobe can be permanent. There is also a risk of a salivary fistula, i.e., the leakage of saliva from the wound. In the vast majority of cases, spontaneous healing occurs here – if not, a Botox injection into the gland can accelerate healing. A long time after a parotidectomy a so-called “gustatory sweating” (Frey syndrome) can rarely occur, in which excessive sweating in the parotid region occurs when eating. If this causes discomfort, a Botox injection can also provide relief.   In submandibulectomy, the removal of the submandibular gland, only the branch of the facial nerve to the corner of the mouth (marginal mandibular nerve) is in the surgical field. Other nerves in the surgical area are the lingual and the hypoglossal nerve, which provide sensory and motor function of the tongue. For both nerves, the risk is extremely low. In the removal of the sublingual gland or resection of tumours of the accessory salivary glands, the risks depend on their location and are often comparable to those of removing an oral cavity tumour.