Salivary gland cancer is a rare malignant neoplasm originating from the cells of the salivary gland. It can affect both large and small salivary glands. It is most often located in the area of the parotid gland. It is manifested by pain, swelling, a feeling of bursting, difficulty swallowing and trying to open your mouth wide. There may be numbness and muscle weakness in the facial area on the affected side. It is characterized by a relatively slow course and predominantly hematogenous metastasis. To confirm the diagnosis, examination data, CT, MRI, PET-CT and biopsy results are used. Treatment – resection or removal of the salivary gland, chemotherapy, radiotherapy.
Meaning
Salivary gland cancer is a rare oncological disease affecting large (parotid, submandibular, sublingual) or small (palatine, lingual, molar, labial, buccal) salivary glands. Data on the prevalence among patients of different ages are ambiguous. Some researchers claim that salivary gland cancer is usually detected in people over 50 years of age. Other experts report that the disease is equally often diagnosed at the age of 20 to 70 years. Salivary gland cancer in patients under 20 years of age accounts for 4% of the total number of cases of the disease. There is a slight predominance of female patients. In 80% of cases, the parotid gland is affected, in 1-7% – one of the small salivary glands, in 4% – the submandibular gland and in 1% – the sublingual gland. The treatment is carried out by specialists in the field of oncology and maxillofacial surgery.
Causes
The causes of salivary gland cancer have not been precisely clarified. Scientists suggest that the main risk factors are adverse environmental influences, inflammatory diseases of the salivary glands, smoking and some eating habits. Harmful environmental influences include radiation exposure: radiation therapy and multiple X-ray examinations, living in areas with high levels of radiation. Many researchers believe that the disease can be provoked by excessive insolation.
There is a connection with occupational hazards. It is noted that salivary gland cancer is more often detected in employees of woodworking, automotive and metallurgical enterprises, hairdressers and asbestos mines. Cement dust, asbestos, chromium, silicon, lead and nickel compounds are indicated as possible carcinogens. Researchers report that the risk of salivary gland cancer increases when infected with certain viruses. For example, a correlation has been established between the prevalence of neoplasia of the salivary glands and the frequency of infection with the Epstein-Barr virus. There is evidence of an increased likelihood of developing salivary gland cancer in patients who have had mumps in the past.
The question of the impact of smoking is still open. According to the results of studies conducted by American scientists, some types of cancer of the salivary glands are more often detected in smokers. However, most experts do not yet include smoking among the risk factors for developing cancer of the salivary glands. Alimentary features include eating food with a high cholesterol content, a lack of vegetable fiber, yellow vegetables and fruits. Hereditary predisposition has not been identified.
Classification
Taking into account the localization , the following types of salivary gland cancer are distinguished:
- Tumors of the parotid glands.
- Neoplasia of the submandibular glands.
- Neoplasms of the sublingual glands.
- Lesions of small (buccal, labial, molar, palatal, lingual) glands.
Taking into account the features of the histological structure, the following types of salivary gland cancer are distinguished: acinous cell adenocarcinoma, cylindroma (adenocystic cancer), mucoepidermoid cancer, adenocarcinoma, basal cell adenocarcinoma, papillary adenocarcinoma, squamous cell carcinoma, oncocytic cancer, cancer of the salivary duct, cancer in pleoform adenoma, other types of cancer.
According to the TNM classification, the following stages of salivary gland cancer are distinguished:
- T1 – a tumor of less than 2 cm in size is determined, not extending beyond the gland.
- T2 – a node with a diameter of 2-4 cm is detected, not extending beyond the gland.
- T3 – the size of the neoplasm exceeds 4 cm or neoplasia extends beyond the gland.
- T4a – cancer of the salivary glands sprouts the facial nerve, the external auditory canal, the lower jaw or the skin of the face and head.
- T4b – neoplasm spreads to the sphenoid bone and the bones of the base of the skull or causes compression of the carotid artery.
The letter N denotes lymphogenic metastases of salivary gland cancer, while:
- N0 – there are no metastases.
- N1 – a metastasis of less than 3 cm in size is detected on the side of the location of salivary gland cancer.
- N2 – a 3-6 cm metastasis is detected / several metastases on the affected side / bilateral / metastases on the opposite side.
- N3 – metastases larger than 6 cm are detected .
The letter M is used to denote distant metastases of cancer of the salivary glands, while M0 – there are no metastases, M1 – there are signs of distant metastasis.
Symptoms
In the early stages, salivary gland cancer may be asymptomatic. Due to the slow growth of neoplasia, nonspecificity and mild severity of symptoms, patients often do not consult a doctor for a long time (for several months or even years). The leading clinical manifestations of salivary gland cancer are usually pain, paralysis of facial muscles and the presence of a tumor-like formation in the affected area. At the same time, the intensity of these symptoms may vary.
In some patients, the first significant sign of salivary gland cancer is numbness and weakness of the facial muscles. Patients turn to a neurologist and receive treatment for neuritis of the facial nerve. Warming up and physiotherapy stimulate the growth of the neoplasm, after a while the node becomes noticeable, after which the patient is referred to an oncologist. In other cases, the first manifestation of salivary gland cancer is local pain with irradiation to the face or ear area. Subsequently, the growing tumor spreads to neighboring anatomical formations, the pain syndrome is joined by spasms of the masticatory muscles, as well as inflammation and obstruction of the auditory canal, accompanied by a decrease or loss of hearing.
When the parotid gland is affected, a soft or densely elastic tumor-like formation with indistinct contours is palpated in the post-maxillary fossa, which can spread to the neck or behind the ear. Germination and destruction of the mastoid process is possible. Salivary gland cancer is characterized by hematogenous metastasis. The lungs are most often affected. The appearance of distant metastases is indicated by shortness of breath, coughing with blood and an increase in body temperature to subfebrile figures. When secondary foci are located in the peripheral parts of the lungs, an asymptomatic or low-symptomatic course is noted.
Salivary gland cancer metastases can also be detected in bones, skin, liver and brain. With bone metastases, pain occurs, with skin lesions in the trunk and extremities, multiple tumor-like formations are detected, with secondary foci in the brain, headaches, nausea, vomiting and neurological disorders are observed. From the moment of the first symptoms to the onset of distant metastasis, it takes from several months to several years. Fatal outcome in salivary gland cancer usually occurs within six months after the occurrence of metastases. Metastasis is more often detected in recurrent cancer of the salivary glands due to insufficient radical surgical intervention.
Diagnostics
The diagnosis is made taking into account anamnesis, complaints, external examination data, palpation of the lesion area, results of laboratory and instrumental studies. A significant role in the diagnosis of salivary gland cancer is played by various imaging methods, including CT, MRI and PET–CT. These techniques allow us to determine the localization, structure and size of salivary gland cancer, as well as to assess the degree of involvement of nearby anatomical structures.
The final diagnosis is established on the basis of aspiration biopsy data and cytological examination of the obtained material. It is possible to reliably determine the type of salivary gland cancer in 90% of patients. To detect lymphogenic and distant metastases, chest x-ray, chest CT, skeleton scintigraphy, liver ultrasound, neck lymph node ultrasound, CT and MRI of the brain and other diagnostic procedures are prescribed. Differential diagnosis is carried out with benign tumors of the salivary glands.
Treatment and prognosis
Therapeutic tactics are determined taking into account the type, diameter and stage of the neoplasm, age and general condition of the patient. The method of choice for salivary gland cancer is combination therapy, which includes surgical interventions and radiotherapy. With small local neoplasms, resection of the gland is possible. With cancer of the salivary glands of large size, complete removal of the organ is necessary, sometimes in combination with excision of the surrounding tissues (skin, bones, facial nerve, subcutaneous tissue of the neck). If lymphogenic metastasis of salivary gland cancer is suspected, the removal of the primary focus is supplemented with lymphadenectomy.
Patients who have undergone extended interventions may subsequently require reconstructive surgery, including skin grafting, replacement of sections of the removed bone with homo- or autografts, etc. Radiation therapy is prescribed before radical surgical interventions or used during palliative treatment of common oncological processes. Chemotherapy is usually used for inoperable cancer of the salivary gland. Cytostatics from the anthracycline group are used. The effectiveness of this method remains insufficiently studied.
The prognosis depends on the location, type and stage of the neoplasm. The average ten–year survival rate for all stages and all types of salivary gland cancer in women is 75%, in men – 60%. The best survival rates are observed in acinous cell adenocarcinomas and highly differentiated mucoepidermoid neoplasia, the worst – in squamous cell tumors. Due to the rarity of lesions of the small salivary glands, statistics for this group of neoplasias are less reliable. Researchers report that 80% of patients with the first stage, 70% – with the second stage, 60% – with the third stage and 30% – with the fourth stage of salivary gland cancer manage to live up to 5 years from the moment of diagnosis.