Salivary gland adenoma is a benign formation that develops from the epithelial cells of the excretory ducts of the small and large salivary glands. It is accompanied by the appearance of a painless rounded node in the projection of the gland. With a significant size of the neoplasm, facial asymmetry, swelling, aching pains, skin paresthesia occur. Adenoma is diagnosed using general clinical and special research methods: ultrasound of the salivary gland, contrast sialography, histology, tomography. Treatment of adenomas is carried out exclusively surgically: depending on the size of the tumor, a complete or partial excision of the gland is performed.
Several histological types of salivary gland adenomas have been described in surgical dentistry. Pleomorphic adenoma is most often diagnosed in clinical practice. It accounts for 50-70% of epithelial neoplasms of large salivary glands (usually parotid) and 20-55% of small (mainly palatine). Adenoma usually occurs in elderly people (after 50-60 years), more often in women.
It grows for a long time ‒ 10-12 years. Pleomorphic adenoma of the salivary gland is also called a mixed tumor because of the morphological heterogeneity of the structure. The neoplasm is benign, but may be malignated. Degeneration into a malignant form occurs in 2-5% of cases. After non-radical treatment, the tumor often recurs.
Reasons of salivary gland adenoma
The etiology of adenoma is not fully understood. There are several theories of the occurrence of the disease: physico-chemical, viral, polyethological. Each theory is valid, but none of them can accurately explain the occurrence of adenoma and cover all the causes of the disease. To date, the most popular and logical is the polyethological concept, according to which the action of various factors can lead to disruption of the cells. Theories of adenoma formation:
- Physico-chemical. It is based on the provision on the triggering role in the process of carcinogenesis of various exogenous substances. Carcinogens include some chemical compounds, ionizing radiation, ultraviolet radiation, exposure to cold. The risk of adenoma formation increases after injury or inflammation of the salivary gland (sialadenitis).
- Viral. Indicates the connection of pathology with the infection of the body with certain viruses (Epstein-Barr, herpes), which provoke the appearance of a tumor. According to this theory, carcinogens create a favorable environment for the invasion and reproduction of oncogenic viruses.
- Polyethological. It is based on the presence of many etiological factors that can cause neoplasm. In addition to the carcinogens and viruses mentioned above, these include gene mutations, violation of the embryonic laying of glands, hormonal disorders, bad habits.
After 45 years, immune and endocrine restructuring occurs in the human body. This condition, combined with a violation of the processes of cell proliferation and differentiation, make the body vulnerable to the development of the tumor process. According to the polyethological theory, under the influence of various factors in the cells of the epithelium of the salivary gland, the processes of cata- and anaplasia occur. There is a violation of the differentiation of cells that begin to multiply uncontrollably, which leads to the formation of adenomas.
Macroscopically, the adenoma is an elastic or dense knot of 5-6 cm in size . The formation is limited to the capsule, but can germinate in the gland tissue. The presence of a capsule and a lobular structure can not always be traced. On the incision, the adenoma may have a whitish, yellowish or gray tint with cartilaginous and mucous components. Microscopically, the adenoma tissue is very heterogeneous, represented by glandular, trabecular, solid-alveolar and microcystic structures, myxoid and hodndroid substance.
Adenomas account for up to 80% of all epithelial neoplasms of the glands. They are characterized by benign growth, slow development, occurrence after 50 years. According to the morphological and histological structure of adenomas, there are the following types:
- Pleomorphic. It is the most common. It is formed from the epithelium of the excretory ducts. Palpationally defined as a round formation with a dense texture and a bumpy surface.
- Monomorphic. The tumor consists mainly of the glandular component of the salivary gland. It has a size of up to 5 cm, soft and elastic when palpated.
- Adenolymphoma. It arises from lymphatic ducts or nodes, contains lymph. It is formed exclusively in the parotid region. It is characterized by clear boundaries, elastic or dense structure, and a tendency to suppuration.
- Oxyphilic (oncocytoma). Occurs in 1% of cases, mainly in the parotid glands. On palpation, it is defined as a clearly bounded elastic nodule.
- Basal cell. It arises from a basaloid type of tissue and contains basal cells. Macroscopically, it is a dense node. It differs from other adenomas in that it never recurs and does not become malignant.
- Canalicular. It appears more often on the mucous membrane of the upper lip or cheek. It consists of prismatic epithelial cells in the form of bundles. It differs in small size, looks like beads.
- Greasy. This is a small nodule consisting of cystic-altered sebaceous cells. The formation is painless, does not recur after removal.
Symptoms of salivary gland adenoma
The formation can occur in any salivary glands: parotid, submandibular, sublingual or small – on the mucous membrane of the lips, cheeks, palate. Pleomorphic adenoma more often affects one of the parotid glands. The tumor appears below the temple, in front of the auricle. Adenoma is characterized by slow growth and long-term existence. Pathognomonic symptoms are the presence of a round or oval seal, clear outlines, mobility and painlessness during palpation.
In the initial stages, the tumor may not bother. As the adenoma grows, unpleasant and painful sensations, swelling, swelling, decreased salivation and dryness in the oral cavity appear. Large tumors can cause facial asymmetry, squeeze surrounding organs, provoke aching pains. Parotid gland adenoma can injure nerve endings, causing skin paresthesia and paralysis of facial muscles.
Large neoplasms cause deformation of the pharynx, which is manifested by unpleasant sensations during eating and swallowing. The defeat of the sublingual glands causes patients to feel a foreign body in the mouth and speech disorders. The tumor of the small salivary glands is characterized by inactivity.
Large adenomas extend beyond the capsule and grow deep into the gland. There is a replacement of the gland tissues and a violation of the function of salivation. There may be lesions of the facial and trigeminal nerves, which threaten neuritis, paresis and muscle paralysis. In the case of untimely and non-radical surgical treatment, the risk of recurrence of adenoma increases significantly.
With the long-term existence of a tumor, 5% of patients experience its malignancy. When an adenoma transforms into a malignant one, a rapid proliferation of tissues occurs, the formation becomes stationary and solid. They are concerned about spontaneous painful sensations, decreased saliva production, dysphagia. In 50% of cases, the malignant neoplasm metastasizes to the lymph nodes.
Diagnostics of salivary gland adenoma
In order to diagnose adenoma, clinical and special research methods are used. The initial examination and interview of the patient is carried out by a dentist-surgeon or oncologist. Differential diagnosis of adenoma is carried out with cysts, lymphadenitis, sialadenitis, malignant tumors of the salivary glands. The following methods of examination and diagnosis are used:
- Inspection and probing. By palpation, the location, structure, shape, mobility, size, contours of the formation are determined; the presence of painful sensations, the ratio of the tumor to the surrounding organs is assessed. Retrograde probing makes it possible to determine the presence of formation in the ducts, the degree of compression of the gland by the tumor. Evaluation of salivary function is performed using a probe and gland massage.
- Contrast radiography. Sialography shows the exact localization and size of the neoplasm in 83%. Benign formations push back the ducts that coincide with the contours of the tumor. According to the contours, the size of the adenoma is judged. Intermittent contrast of the ducts is characteristic of malignant formations.
- Echography. Ultrasound of the salivary glands allows us to judge the size of the tumor and its structure. Echogenicity determines the structural changes of the gland, the degree of replacement by connective tissue. Benign formations have smooth and clear contours. The study is less accurate with a deep location of the adenoma.
- Histological and cytological examination. They are performed after aspiration biopsy and receiving tumor punctures. They allow to verify the tumor, clarify the cellular composition, determine the type of adenoma, differentiate benign and malignant formations.
- Tomography. CT and MRI of the salivary glands provide accurate and complete information about the disease. Computer and magnetic resonance imaging have the highest diagnostic value, show the ratio of the tumor to the surrounding tissues, the stage of development, specify the topographic and anatomical localization.
Treatment of salivary gland adenoma
Treatment is carried out mainly surgically. The method of surgery depends on the clinical course of the disease, the size and location of the adenoma, the age and state of health of the patient. The most difficult thing to remove is the parotid adenoma, which is due to the complex anatomy of this area. During the operation, it is important to correctly isolate and preserve the facial nerve. The following methods of surgical intervention are used in maxillofacial surgery:
- Tumor enucleation. Removal of the adenoma involves the peeling and elimination of the tumor within its shell. Dissection of the gland capsule is performed, the tumor shell is detached from the surrounding tissues around the perimeter. The neoplasm is gradually dissected and removed. The method is the least traumatic.
- Excision of the gland. Parotidectomy can be partial (removal of the tumor and a small underlying part of the gland), subtotal (extirpation of the adenoma together with several lobes of the gland) and total (extirpation of the parotid gland with a tumor). With pleomorphic adenoma, experts recommend a total parotidectomy, because the formation is prone to malignancy and recurrence. Modern technologies allow performing the operation using a laser, a microscope and computer technology. The intervention is carried out with little trauma, and the rehabilitation period is easier.
Prognosis and prevention
After surgical removal of the adenoma, the prognosis for life and health is favorable. The postoperative period lasts 7-10 days. Complications after surgical treatment are extremely rare. After total parotidectomy, the possibility of recurrence is reduced to 1-4%. In case of repeated formation of an adenoma, surgical intervention is carried out again in a more radical volume. There is no specific prevention of the disease. General preventive measures include the prevention of carcinogenic effects, diseases of the salivary glands, traumatic injuries, compliance with the principles of a healthy diet and lifestyle.