Salivary gland tumor overview

# Overview
Salivary gland tumor is a tumor that forms in the tissues of a salivary gland. The salivary glands are classified as major and minor. The major salivary glands consist of the parotid, submandibular, and sublingual glands. The minor glands include small mucus-secreting glands located throughout the palate, nasal, and oral cavity. Malignant salivary gland neoplasms account for approximately 0.5% of all malignancies and approximately 3% to 5% of all head and neck tumors.
Salivary gland tumor may be classified according to the World Health Organization into five groups: malignant epithelial tumors, benign epithelial tumors, soft tissue tumors, hematolymphoid tumors, and secondary tumors. The pathophysiology of salivary gland tumors depends on the histological subtype. There are no established causes of salivary gland tumors. The incidence of salivary gland tumors is approximately 2.5 to 3.0 individuals per 100,000 individuals worldwide. The incidence of salivary gland tumors is estimated to be 2000 to 2500 cases per year in the United States. The incidence of salivary gland tumors increases with age; the median age at diagnosis is 64 years. Salivary gland tumors are more common in males than females. There is no racial predilection to the salivary gland tumors. Common risk factors in the development of salivary gland tumors are age, radiation exposure, environment and occupational exposure, certain viruses, male gender, smoking, and family history. Symptoms of salivary gland tumor includes difficulty swallowing, muscle weakness on one side of the face, a lump or swelling on or near the jaw or in the neck or mouth, numbness in part of the face, persistent pain in the area of a salivary gland, and trouble opening the mouth widely. The optimal therapy for salivary gland tumors depends on the stage at diagnosis. The mainstay of therapy for salivary gland tumors is surgery. External beam radiation therapy may be used following surgery, when surgery is not possible, or would cause significant complications. Chemotherapy is considered when radiation therapy or surgery is not possible.

# Classification
Salivary gland tumor may be classified according to the World Health Organization into five groups: malignant epithelial tumors, benign epithelial tumors, soft tissue tumors, hematolymphoid tumors, and secondary tumors.

# Pathophysiology
The pathophysiology of salivary gland tumors depends on the histological subtype.

# Causes
There are no established causes of salivary gland tumors.

# Differential Diagnosis
Salivary gland tumor must be differentiated from other diseases that cause a salivary gland mass or enlargement such as salivary cysts, cysts of the first branchial cleft, salivary gland stones, sarcoid infiltration of the parotid gland, Sjogren's syndrome, metastasis from other tumors, lymphoepithelial cysts, chronic sclerosing sialadenitis, regional lymphadenopathy, Bell's palsy, and intraparotid facial nerve schwannoma.

# Epidemiology and Demographics
The incidence of salivary gland tumors is approximately 2.5 to 3.0 cases per 100,000 individuals worldwide. The incidence of salivary gland tumors is estimated to be 2000 to 2500 cases per year in the United States. The incidence of salivary gland tumors increases with age; the median age at diagnosis is 64 years. Salivary gland tumors are more common in males than females. There is no racial predilection to the salivary gland tumors.

# Risk Factors
Common risk factors in the development of salivary gland tumors are age, radiation exposure, environment and occupational exposure, certain viruses, male gender, smoking, and family history.

# Screening
According to the United States Preventive Services Task Force, screening for salivary gland tumors is not recommended.

# Natural History, Complications and Prognosis
If left untreated, patients with salivary gland tumors may progress to develop metastasis. Common complications of salivary gland tumors include metastasis, injury to the facial nerve, and Frey's syndrome. Prognosis is generally good, and the 5 year mortality rate of patients with salivary gland cancer that has not spread at the time of diagnosis is 91%.

# Staging
According to the TNM staging system by the American Joint Committee on Cancer, there are four stages of salivary gland cancers based on the tumor size, lymph nodes involved, and metastasis.

# History and Symptoms
Symptoms of salivary gland tumor includes dysphagia, muscle weakness on one side of the face, a lump or swelling on or near the jaw or in the neck or mouth, numbness in part of the face, persistent pain in the area of a salivary gland, and trouble opening the mouth widely.

# Physical Examination
Common physical examination findings of salivary gland  cancer include painless, firm swelling in one of the salivary gland, cervical lymphadenopathy, dysphagia, trouble opening the mouth widely, difficulty moving one side of the face and muscle weakness on one side of the face suggestive of cranial nerve VII deficit, loss of corneal reflex, localized or regional pain, numbness, paresthesia, causalgia, or a loss of motor function suggestive of cranial nerve V deficit.

# Laboratory Findings
There are no established lab findings associated with salivary gland tumors.

# Fine Needle Aspiration Biopsy (FNAB)
Biopsy of the tumor tissue is diagnostic of salivary gland tumor.

# Head X ray
X-rays of jaw and teeth may be helpful in the diagnosis of salivary gland tumor.

# CT
Head and neck CT scan may be diagnostic of salivary gland tumors. Findings on CT scan suggestive of salivary gland tumors include bony, local and, perineural invasion, and lymph node metastasis.

# MRI
Head and neck MRI may be diagnostic of salivary gland tumors. Findings on head and neck MRI suggestive of salivary gland tumors include soft tissue infiltration, perineural invasion, and intracranial extention.

# Ultrasound
Ultrasound may be helpful in the diagnosis of salivary gland tumors. Findings on ultrasound suggestive of salivary gland tumors typically includes hypoechoic mass with lobulated distinct border with or without posterior acoustic enhancement. Ultrasound is also useful in guiding biopsy including FNAC and core biopsies.

# Other Imaging Studies
Other imaging studies for salivary gland tumor include PET scan and endoscopy.

# Other Diagnostic Studies
There are no other diagnostic studies associated with salivary gland tumors.

# Medical Therapy
The optimal therapy for salivary gland tumors depends on the stage at diagnosis. The mainstay of therapy for salivary gland tumors is surgery. External beam radiation therapy may be used following surgery, when surgery is not possible (e.g. high risk of complication). Chemotherapy is considered when radiation therapy or surgery is not possible.

# Surgery
The mainstay of therapy for salivary gland tumor is surgery.

# Primary Prevention
Effective measures for the primary prevention of salivary gland tumors include avoiding some of the possible risk factors such as tobacco, and excess alcohol use.

# Secondary Prevention
Secondary prevention strategies following salivary gland cancer include follow-up visits every 6-8 weeks for the first year, every 2-3 months in the second year, every 3-4 months in the third year, and then every 6-12 months for life.