A malignant neoplasm of the parotid gland refers to a cancerous tumor that originates in one of the parotid glands. These glands are the largest of the salivary glands, situated on each side of the face, just below and in front of the ears. The tumor cells are abnormal and can grow uncontrollably, invade surrounding tissues, and spread to other parts of the body. While most parotid gland tumors are benign, a significant portion can be cancerous.
Recognizing the Signs
A common sign of a parotid gland malignant neoplasm is a lump or swelling on one side of the face, typically near the ear or cheek. While many parotid lumps are painless, pain can suggest a cancerous tumor, particularly if it indicates nerve invasion. Rapid growth of the mass is also a concerning symptom.
Facial weakness or paralysis on the affected side is another symptom, occurring in 7% to 20% of patients with malignant parotid tumors. This symptom rarely associates with benign lesions and often suggests involvement of the facial nerve, which passes through the parotid gland. Difficulty opening the mouth widely (trismus) may also occur, often indicating advanced disease where the tumor has extended into the masticatory muscles. Difficulty swallowing or a feeling of a foreign body in the throat can point to a tumor in the deeper part of the gland.
Diagnosis and Classification
Diagnosis begins with a physical examination, where a healthcare provider feels the jaw, neck, and throat for lumps or swelling. Imaging techniques then visualize the tumor. Ultrasound provides information on the tumor’s size, shape, and border definition. Magnetic Resonance Imaging (MRI) and Computed Tomography (CT) scans offer comprehensive images, showing the tumor’s exact location, size, and its relationship to surrounding structures like muscles, blood vessels, and nerves.
A Positron Emission Tomography (PET) scan may also detect cancer spread to other parts of the body. Definitive diagnosis relies on a biopsy, where a tissue sample is removed for laboratory testing.
Fine needle aspiration (FNA) biopsy involves inserting a thin needle into the tumor to draw out cells and fluid. A core needle biopsy collects a larger tissue sample and is considered more accurate. These biopsies help classify the tumor, as there are various types of malignant parotid tumors, such as mucoepidermoid carcinoma and adenoid cystic carcinoma, each with distinct biological behaviors. Mucoepidermoid carcinoma is the most common malignant tumor of the parotid gland, accounting for about 30% of parotid malignancies. This classification guides the treatment plan.
Treatment Options
Surgery is the primary treatment for malignant neoplasms of the parotid gland, aiming to remove the tumor completely while preserving healthy tissue. The extent of surgery, known as a parotidectomy, varies from superficial parotidectomy (removing only the outer part of the gland) to total parotidectomy (removing the entire gland). If the facial nerve is involved or its function is impaired, surgical removal may involve sacrificing the nerve, though nerve-grafting procedures can sometimes be used for repair.
Radiation therapy is frequently used after surgery to reduce the risk of cancer recurrence, particularly if surgical margins are close or positive, if the tumor is high-grade, or if there is evidence of perineural or lymphovascular invasion. It may also be the main treatment option if the tumor is too large to remove surgically, is in a difficult position, or if a patient’s health precludes surgery. External radiation therapy, directing high-energy X-rays from outside the body, is the most common type for salivary gland cancer.
Chemotherapy is generally reserved for advanced or metastatic cases, meaning the cancer has spread to distant parts of the body. While chemotherapy drugs can help shrink tumors and manage symptoms, they are not typically curative for salivary gland cancers. In some instances, chemotherapy may be combined with radiation therapy (chemoradiation) to make cancer cells more sensitive to radiation, especially for aggressive tumors or those that have spread to nerves or lymph nodes. Treatment plans are highly individualized and often involve a multidisciplinary team of specialists to determine the most effective approach.
Outlook and Long-Term Care
The outlook for individuals with malignant parotid gland neoplasms is influenced by several factors, including the tumor’s stage, type, and grade. Early diagnosis generally leads to better outcomes. Tumors confined to the parotid gland at diagnosis tend to have a better prognosis than those that have spread to nearby structures or distant sites. For instance, the five-year survival rate for localized salivary gland cancer is approximately 94%, while for advanced metastatic cancer, it is around 44%. The specific tumor type also impacts the long-term outlook, with some types, like salivary ductal carcinoma, being associated with earlier recurrence, while others, such as adenoid cystic carcinoma, may have later recurrences.
After treatment, regular follow-up appointments are important for surveillance and to monitor for recurrence. These appointments may involve physical examinations and imaging tests.
Long-term considerations include managing treatment side effects, such as facial nerve issues if the nerve was affected during surgery, or dry mouth (xerostomia) if radiation therapy was administered. Supportive care, including rehabilitation, may be recommended to address functional impairments. Patients should promptly report any new lumps or changes to their healthcare provider.