Salivary gland neoplasm

Salivary gland cancer is a cancer that forms in 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. Salivary gland cancer is rare, with 2% of head and neck tumors forming in the salivary glands, the majority in the parotid.

Classification


Salivary gland neoplasms are classified by the World Health Organization as primary or secondary, benign or malignant, and by tissue of origin. This system defines five broad categories of salivary gland neoplasms:
 * malignant epithelial tumors (e.g. acinic cell carcinoma, mucoepidermoid carcinoma and adenoid cystic carcinoma, salivary duct carcinoma)
 * benign epithelial tumors (e.g. pleomorphic adenoma, myoepithelioma and Warthin tumour, sebaceous lymphadenoma)
 * soft tissue tumors (Hemangioma)
 * hematolymphoid tumors (e.g. Hodgkin lymphoma)
 * secondary tumors.

Signs and symptoms
Signs include fluid draining from the ear, pain, numbness, weakness, trouble swallowing, and a lump. The most common symptom of major salivary gland cancer is a painless lump in the affected gland, sometimes accompanied by paralysis of the facial nerve.

Causes
The chief risk factor is chewing tobacco, followed by smoking. Other risk factors include older age, radiation therapy treatment to head or neck, and being exposed to certain carcinogenic substances at work.

Diagnosis
In most cases, local excision with a margin of normal tissue is the appropriate form of biopsy for a major salivary gland tumor. In the parotid region, this requires identification of the facial nerve. For submandibular tumors, the entire submandibular triangle is cleared. In contrast, minor salivary gland tumors have a higher likelihood of being malignant, and an incisional biopsy is performed initially so that definitive treatment can be planned. In the parotid region, the presence of pain, recent rapid enlargement of a preexisting nodule, skin involvement, or facial nerve paralysis suggests cancer. Enlarged cervical lymph nodes in association with a salivary gland tumor are considered a manifestation of cancer until proved otherwise. Fine-needle aspiration is indicated if accurate diagnosis will allow for better treatment planning.

Treatment
Treatment may include the following:
 * Surgery with or without radiation.
 * Radiation therapy.
 * Chemotherapy.

Radiotherapy
Fast neutron therapy has been used successfully to treat salivary gland tumors, and has shown to be significantly more effective than photons in studies treating unresectable salivary gland tumors.