About The Salivary Glands
There are three paired glands in the head and neck that produce saliva. The parotid glands are the largest and overlie the angle of the jaw in front of the ear. A tube, known as Stensen’s duct, drains saliva from the glands into the mouth. The submandibular glands lie deep to the lower jaw and their ducts, which are the longest and narrowest of all the salivary glands, enter the mouth under the front of the tongue. The sublingual glands lie deep to the lining of the mouth on each side of the tongue, these glands have many short ducts that enter the mouth directly through the lining.
In addition to these major glands there are hundreds of minor salivary glands throughout the lining of the mouth and throat with most on the lips and palate. All of these glands produce saliva in response to food being placed in the mouth.
Salivary Gland Tumours
Benign tumours are the most common and present as a firm to hard, mobile, regular mass without involvement of overlying or deep structures. They tend to enlarge slowly and progressively and they are painless. Malignant tumours on the other hand can enlarge rapidly, they can become fixed to underlying structures or the subcutaneous tissue and skin overlying the gland. They can involve nerves associated with the salivary gland and can spread to lymph nodes in the neck.
Tumours in the parotid gland are 80% likely to be benign, whereas submandibular tumours are only 50% likely to be non cancerous. In the sublingual gland and minor salivary glands most neoplasms are malignant.
1. Parotid Gland Tumours
Most lumps of the parotid are benign. The most common is the pleomorphic adenoma followed by Warthins Tumour. They present as a firm mobile mass in the face or upper neck. They can become quite large if left to grow. The majority 90% of these tumours occur in the superficial aspect of the gland (lateral to the nerve of the face) occasionally , however, these tumours occur in the deep part of the gland, behind the jaw. Benign salivary gland tumours generally do not cause facial weakness. Pleomorphic adenomas have a risk of malignant change over a long period of time.
The most common malignant tumour (70%) of the parotid gland in Australia is spread of skin cancer involving intra-parotid lymph nodes. These tend to be aggressive tumours that may also spread to lymph nodes in the neck. There is usually a history of removal of a skin cancer or melanoma on the scalp, ear, facial or temple skin in the preceding two years. Occasionally a patient will present with a lump that originates in the parotid. These also tend to be hard and irregular and can be fixed to deep structures or to the overlying skin causing discolouration or ulceration. They can be multiple and there can be palpable lymph nodes in the neck most frequently in the upper deep cervical region.
2. Submandibular Tumours
Tumours in the submandibular gland are equally likely to be benign or malignant. They usually present as a firm to hard mass within the gland. Usually mobile and tend only to become fixed and involve nerves if malignant. Skin cancers and melanoma can spread to nodes in this region also, however the lymph nodes are not within the substance of the gland like the parotid gland but attached to the fascia around the gland.
Minor Salivary Gland Tumours Uncommon and more likely (50%-80%) to be malignant. Present as a submucosal lump on the oral or nasal mucosa. Most common on the palate, lip, tongue and floor of mouth.
Clinical assessment is very important in the diagnosis of salivary gland masses. Investigations are not always necessary and in fact can lead to a false sense of security and adoption of conservative management when surgery is required. There is however a role for investigating some parotid and other salivary gland tumours.
Overall physical examination, imaging and Fine Needle Aspirate (FNA) is adequate for a diagnosis in approximately 95% of masses.
Surgery is required for all salivary tumours with the only exceptions being a probable benign tumour in an older patient who is reluctant for surgery or is an anaesthetic risk. Even with a tumour that is suspected to be benign on investigation the rationale for operating is threefold. 1. All tumours progress and the risk to the surrounding structures are greater with larger tumours. 2. It can be difficult to diagnose malignancy clinically and there is a false negative rate with needle biopsy. 3. Benign salivary tumours are at risk of malignant transformation.
Parotid Gland Surgery (Parotidectomy)
The operation is performed under general anaesthetic. An incision is made in front of the ear it passes down behind the ear lobe and then curves forward into the neck. It is a similar incision to that used for a cosmetic facelift, it heals well and is rarely noticeable. The wound is carefully closed at the end of the operation and a suction drain is placed to remove any blood or fluid that would otherwise collect under the skin.
The operation varies depending on the type, position and size of the tumour. For the majority of parotid tumours only a portion of the gland containing the tumour is removed. If the tumour involves the deep lobe, then a greater portion is removed. With some deep lobe parotid tumours the jaw may need to be opened to allow access to the deep part of the tumour. Occasionally and only with advanced malignant tumours the facial nerve needs to be removed.
With metastatic skin malignancy and some high grade salivary cancers where lymph nodes are involved removal of neck lymph nodes is also necessary. This operation is called a neck dissection.
Post operatively one to two nights in hospital are required and normal activities can be resumed in one to two weeks.
Submandibular Gland Surgery
This operation is also best performed under general anaesthetic. The incision is made in the neck about two finger breadths below the lower border of the jaw in a skin crease. The wound usually heals very well and after a period is almost imperceptible. A drain is also used in this operation.
The entire gland is removed also with a small portion of the duct. If there is a malignant tumour a wider excision is often required with removal of surrounding soft tissue or jaw bone including muscle, lymph nodes and occasionally surrounding nerves. In metastatic skin malignancy and some high-grade salivary cancers with lymph node involvement removal of lymph nodes in the neck is also necessary. This operation is called a neck dissection and is explained in another article.
Post operatively one to two nights in hospital is usually necessary and normal activities may often be resumed in one to two weeks.