What are salivary glands?
The salivary glands are exocrine glands of the upper digestive system that produce and release saliva into the oral cavity.
These glands are classified according to their size and functional importance into:
- Major salivary glands: include the sublingual glands, the parotid glands, and the submaxillary glands (Fig. 1).
- Minor, secondary or accessory salivary glands: they are distributed in the mucosa and submucosa of the organs of the mouth and are the labial, genian, palatine and lingual glands.
What types of tumors affect the salivary glands?
80% of salivary tumors occur in the parotid gland, 10 to 15% in the submaxillary gland and 5 to 10% in the sublingual and minor salivary glands. The smaller the size of the salivary gland, the more likely a tumor is to be malignant.
Benign tumors
- Pleomorphic adenoma: represents 80 to 90% of benign neoplasms. It appears between 40 and 50 years of age. It is a well-demarcated tumor with a pseudocapsule and multiple nodules protruding from the main mass as pseudopod foci. This feature explains its high recurrence rate when the tumor is simply enucleated. Recurrent tumors have a high tendency to be multinodular. Only 0.5% of pleomorphic adenomas are multicentric.
- Warthin’s tumor: it represents the second most likely tumor of the salivary glands. It constitutes 5 to 7% of benign tumors. It appears exclusively in the parotid gland, where it usually manifests as a slow-growing mass in the inferior extension. In 12% of cases it is bilateral.
- Other less frequent benign tumors: Myoepithelioma, monomorphous adenoma, basal cell adenoma, oncocytoma, etc.
Malignant tumors
- Low malignancy tumors: includes acinic cell tumor, low malignancy mucoepidermoid carcinoma, adenocystic carcinoma (cylindroma) and malignant pleomorphic adenoma.
- High malignancy tumors: include high malignancy mucoepidermoid carcinoma, adenocarcinoma, anaplastic carcinoma, salivary gland metastasis (originating from epidermoid skin carcinoma or melanoma).
What is the diagnosis?
Clinical evaluation is the first diagnostic step: salivary tumors are usually palpable rather than visible.
There are criteria (Rankow’s) which, independently of the histological excision of the tumor, usually lead to the suspicion of a benign or malignant tumor:
Paralysis of the facial nerve associated with a parotid tumor is an unequivocal sign of malignant neoplasm and worsens its prognosis. In some statistics, survival at 5 years reaches only 10% of cases and at 10 years mortality is 100%.
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Histopathological diagnosis
Currently, fine needle aspiration puncture (FNA) is usually satisfactory to guarantee obtaining material that offers an accurate diagnosis. In experienced hands it has an accuracy of between 90 and 95%.
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Radiological study
Depending on the histopathological characteristics of each case, extension studies by CT and/or MRI will be necessary (Fig. 2).
Surgical treatment
The surgical treatment to be used varies depending on whether it is the parotid gland or the submaxillary gland:
Parotid gland
- When it is a benign tumor located in the superficial lobe of the parotid gland the best treatment is surgical excision with safety margins (conservative suprafacial parotidectomy or Extracapsular Dissection, ECS), with better results (lower recurrence rate) than simple tumor enucleation.
- Benign tumors that are located in or affect the deep lobe of the parotid should be treated by total parotidectomy (Fig. 2).
- In malignant tumors, as a general principle, as wide an excision as possible should be performed, with the aim of obtaining margins free of infiltration. The treatment of choice is total parotidectomy with preservation of the facial nerve, whenever possible. In the case of a malignant tumor, depending on the histology and size of the tumor, cervical lymph node emptying is indicated.
Submaxillary gland
- A submandibular sialadenectomy is performed, which consists of making an incision below the jaw line to access the gland and remove it. In the case of a malignant tumor, depending on the histology and size of the tumor, cervical lymph node emptying is indicated.