AUTHOR AND EDITOR INFORMATION

Section 1 of 10  

• Authors and Editors
• Introduction And Anatomy
• Diagnosis
• Pathology
• Operative Management
• Reconstruction
• Adjunctive Therapy
• Prognosis
• Surveillance
• References

INTRODUCTION AND ANATOMY

Section 2 of 10  

• Authors and Editors
• Introduction And Anatomy
• Diagnosis
• Pathology
• Operative Management
• Reconstruction
• Adjunctive Therapy
• Prognosis
• Surveillance
• References

Parotid glands are the largest salivary glands in humans and are frequently involved in disease processes. Approximately 25% of parotid masses are nonneoplastic; the remaining 75% are neoplastic. Nonneoplastic causes of parotid mass include cysts, parotitis, lymphoepithelial lesions associated with AIDS, collagen vascular diseases, and benign hypertrophy.

Benign hypertrophy is encountered in patients with bulimia, sarcoidosis, sialosis, actinomycosis infections, and mycobacterial infections. Of the 75% of parotid masses that are neoplastic, 75% of these are benign and are discussed in the eMedicine article Parotid Tumors, Benign.

The paired parotid glands are formed as epithelial invaginations into the embryological mesoderm and first appear at approximately 6 weeks' gestation. The glands are roughly pyramidal, with the main body overlying the masseter muscle.

The glands extend to the zygomatic process and mastoid tip of the temporal bone and curve around the angle of the mandible to extend to the retromandibular and parapharyngeal spaces. The parotid duct exits the gland medially, crosses the superficial border of the masseter, pierces the buccinator, and enters the oral cavity through the buccal mucosa opposite the second maxillary molar.

The gland is divided into superficial and deep lobes with regard to its relation to the facial nerve, which travels through the gland. This division is not truly anatomic but rather is used for surgical treatment of parotid masses. Fortunately, most parotid malignancies arise in the superficial lobe.

The facial nerve exits the cranium via the stylomastoid foramen and courses through the substance of the parotid gland. The superficial lobe of the parotid rests superficial to or lateral to the facial nerve, whereas the deep lobe rests deep to or medial to the facial nerve. The facial nerve branches within the substance of the parotid gland, and the branching pattern is highly variable.

Numerous lymph nodes also are present within the parotid gland, subsequently draining to preauricular, infra-auricular, and deep upper jugular nodes.

DIAGNOSIS

Section 3 of 10  

• Authors and Editors
• Introduction And Anatomy
• Diagnosis
• Pathology
• Operative Management
• Reconstruction
• Adjunctive Therapy
• Prognosis
• Surveillance
• References

Evaluation of a patient with a suggested parotid gland neoplasm must begin with a thorough medical history and physical examination.

The most common presentation is a painless, asymptomatic mass. More than 80% of patients present because of a mass existing in the cheek. Approximately 30% will relate pain associated with the mass, although most malignancies are painless. Pain most likely indicates perineural invasion, which greatly increases the suggestion of malignancy.

Of these patients, 7-20% present with facial nerve paralysis, which almost never accompanies benign lesions and indicates a grave prognosis. Approximately 80% of patients with facial nerve paralysis have nodal metastasis at the time of diagnosis. These patients have an average survival of 2.7 years and a 10-year survival of 14-26%.

Other important aspects of the history include length of time the mass has been present and history of prior cutaneous lesion or parotid lesion excision. Slow-growing masses of long-standing duration tend to be benign. A history of prior squamous cell carcinoma, malignant melanoma, or malignant fibrous histiocytoma suggests intraglandular metastasis or metastasis to parotid lymph nodes. Prior parotid tumor most likely indicates a recurrence because of inadequate initial resection.

Trismus often indicates advanced disease with extension into the masticatory muscles or invasion of the temporomandibular joint. Dysphagia or a sensation of a foreign body in the oropharynx indicates a tumor of the deep lobe of the gland. A report of ear pain may indicate extension of the tumor into the auditory canal. The presence of numbness in the distribution of the second or third divisions of the trigeminal nerve often indicates neural invasion.

Physical examination of the head and neck must be thorough and complete. The entire head and neck must be examined for cutaneous lesions, which may be caused by metastasis from the parotid gland or parotid nodes.

• Palpation of the mass should determine the degree of firmness. Even benign tumors are usually firm, but a rock-hard mass generally denotes malignancy.
• Skin fixation, skin ulceration, or fixation to adjacent structures also indicates malignancy. The external auditory canal must be visualized for tumor extension.
• All regional nodes must be carefully palpated to detect nodal metastasis. Examination of the oral cavity and oropharynx also may yield further evidence of metastasis or malignant nature of the lesion.
• Blood or pus from Stenson duct are signs of malignancy but are infrequently encountered. More often, one may see bulging of the lateral pharyngeal wall or soft palate, indicating tumor in the deep lobe of the gland.
• Bimanual palpation with one finger against the lateral pharyngeal wall and the other against the external neck may confirm extent into the tonsillar fossa and soft palate.

Once a thorough history and physical examination are complete, perform diagnostic procedures to confirm the diagnosis and extent of the disease process.

Fine needle aspiration

• Fine needle aspiration of the mass or a suggestive lymph node may be performed to obtain a tissue diagnosis.
• The sensitivity of this procedure is greater than 95% in experienced hands. However, only a positive diagnosis should be accepted; negative results indicate the need for further attempts at obtaining a histologic diagnosis, including repeat fine needle aspiration.
• The results of the fine needle aspiration provide a histologic diagnosis and assist in preoperative planning and patient counseling but cannot distinguish benign from malignant epithelial lesions. This is because malignancy of parotid epithelial cells is related to the behavior of the tumor cells in relation to tissue planes and surrounding structures rather than cellular architecture, which may be rather normal even in malignancy. Therefore, nonepithelial lesions may be diagnosed with accuracy, but epithelial lesions require further investigation.
• If fine needle aspiration is unsuccessful in obtaining a diagnosis, an incisional biopsy should not be performed. This procedure has a high rate of local recurrence and places the facial nerve at risk for injury from inadequate visualization.
• Some authors advocate large core needle biopsies, but this procedure is less popular because of potential facial nerve injury and theoretical seeding of the needle tract with tumor cells.
• If performed, the needle should be inserted so that the tract may be excised during the definitive operation. When all attempts at obtaining a histologic diagnosis have failed, operative exploration should proceed after appropriate imaging studies have been obtained.
• Intraoperatively, a frozen section of the specimen should be submitted for diagnosis. The use of frozen sections has demonstrated greater than 93% accuracy in the diagnosis of parotid malignancy.

Imaging studies

• Imaging studies are very helpful in staging and surgical planning. Sialography is mentioned for historic interest only. Although it may help differentiate inflammatory versus neoplastic processes, sialography is infrequently performed and is of limited value in the evaluation of parotid masses.
• Sonography may be beneficial in that benign lesions are of lower density and have smaller caliber blood vessels. However, determination of a cystic component may be misleading, because cystic degeneration may occur as a result of necrosis at the avascular center of a malignancy.
• CT scan and MRI have become invaluable tools in the evaluation of parotid malignancies.
• MRI demonstrates the mass in greater contrast than CT scan, but CT scanning provides better detail of the surrounding tissues. These imaging studies may identify regional lymph node involvement or extension of the tumor into the deep lobe or parapharyngeal space.
• CT scan criteria for lymph node metastasis include any lymph node larger than 1-1.5 cm in greatest diameter, multiple enlarged nodes, and nodes displaying central necrosis.
• Lymph nodes harboring metastasis also may appear round rather than the normal kidney bean shape, and evidence of extracapsular extension may be identified.

PATHOLOGY

Section 4 of 10  

• Authors and Editors
• Introduction And Anatomy
• Diagnosis
• Pathology
• Operative Management
• Reconstruction
• Adjunctive Therapy
• Prognosis
• Surveillance
• References

Many types of parotid malignancies exist, and most of them arise from the epithelial elements of the gland. Classification of these can be quite confusing. In addition, malignancy may develop in the secretory element of the gland, and malignancy arising elsewhere first may be noticed as a metastasis to the gland.

Mucoepidermoid carcinoma

• Mucoepidermoid carcinoma is the most common malignant tumor of the parotid gland, accounting for 30% of parotid malignancies.
• Limited local invasiveness and low metastatic potential characterize this tumor. If metastatic, it is most likely to metastasize to regional nodal basins rather than to distant locations.
• For patients with low-grade tumors without nodal or distant metastasis, 5-year survival approaches 75%, whereas patients with high-grade tumors with lymph node metastasis at the time of diagnosis have a 5-year survival of only 5%. Overall 10-year survival is 50%.

Adenoid cystic carcinoma

• The adenoid cystic carcinoma is characterized by its unpredictable behavior. It possesses a highly invasive quality but may remain quiescent for a long time.
• This tumor may be present for more than 10 years and demonstrate little change and then suddenly infiltrate the adjacent tissues extensively. The tumor also has an affinity for growth along perineural planes and may demonstrate skip lesions along involved nerves.
• Metastasis is more common to distant sites than to regional nodes, with lung metastases being most frequent. This tumor has the highest incidence of distant metastasis, occurring in 30-50% of patients.
• Three histologic types have been identified: cribrose, tubular, and solid.
• The solid form has the worst prognosis; the cribrose pattern possesses the most benign behavior and best prognosis. This tumor requires aggressive initial resection. Overall 5-year survival is 35%, and 10-year survival is approximately 20%.

Malignant mixed tumors

• Malignant mixed tumors arise most commonly as a focus of malignant degeneration within a preexisting benign pleomorphic adenoma (carcinoma ex pleomorphic adenoma).
• However, these also may develop de novo (carcinosarcoma). The longer pleomorphic adenoma has been present, the greater the chance of carcinomatous degeneration.
• Carcinosarcomas, true malignant mixed tumors, are rare. Overall 5-year survival is 56%, and 10-year survival is 31%.

Acinic cell carcinoma

• It is an intermediate-grade malignancy with low malignant potential. This tumor may be bilateral or multicentric and is usually solid, rarely cystic.
• Although this tumor rarely metastasizes, occasional late distant metastases have been observed. This tumor also may spread along perineural planes. Overall 5-year survival is 82%, and 10-year survival is 68%.

Adenocarcinoma

• Adenocarcinoma of the parotid develops from the secretory element of the gland. This is an aggressive lesion with both local lymphatic and distant metastatic potential.
• Approximately 33% of patients have nodal or distant metastasis present at the time of initial diagnosis. Overall 5-year survival is 19-75%, as it is highly variable and related to grade and stage at presentation.

Sebaceous carcinoma is a rare parotid malignancy often presenting as a painful mass and commonly involving the overlying skin.

Salivary duct carcinoma is a rare and highly aggressive tumor. Small cell carcinoma exists as 2 types. The ductal cell origin type is mostly benign and rarely metastasizes. The neuroendocrine origin type is often aggressive and has higher metastatic potential.

Lymphoma

• The parotid gland also may be the site of occurrence of lymphoma, most commonly in elderly males. This is also observed in approximately 5-10% of patients with Warthin tumor of the parotid gland, a benign neoplasm.
• The entire parotid is typically enlarged with a rubbery consistency on palpation. Often, regional nodes also are enlarged. Biopsy of enlarged regional nodes avoids unnecessary parotid surgery, as the definitive treatment consists of chemotherapy or radiation therapy.

The parotid also may be the site of metastasis from cutaneous, renal, lung, breast, prostate, or GI tract malignancies.

Primary squamous cell carcinoma of the parotid is rare, and metastasis from other sites must be excluded. Overall 5-year survival is 21-55%, and 10-year survival is 10-15%.

OPERATIVE MANAGEMENT

Section 5 of 10  

• Authors and Editors
• Introduction And Anatomy
• Diagnosis
• Pathology
• Operative Management
• Reconstruction
• Adjunctive Therapy
• Prognosis
• Surveillance
• References

The current therapy for parotid malignancy is aggressive surgical resection followed by radiation therapy when indicated. Conservative excisions are plagued by a high rate of local recurrence. The extent of resection is based on tumor histology, tumor size and location, invasion of local structures, and the status of regional nodal basins.

Most tumors of the parotid (approximately 90%) originate in the superficial lobe. Superficial parotid lobectomy is the minimum operation performed in this situation. This procedure is appropriate for malignancies confined to the superficial lobe, those that are low grade, those less than 4 cm in greatest diameter, tumors without local invasion, and those without evidence of regional node involvement.

Surgical resection procedure

The most important initial step is identification of the facial nerve and its course through the substance of the parotid gland. To assist in this maneuver, some authors use a nerve stimulator and avoid the use of paralytic anesthetic agents. This is not usually necessary in the primary setting, but recurrent resections may be very difficult and probably should be performed in this manner.

• Ideally, the dissection of the facial nerve should be performed without disturbing or violating the tumor. The facial nerve may be found exiting the stylomastoid foramen by reflecting the parotid gland anteriorly and the sternocleidomastoid muscle posteriorly.
• The cartilaginous external auditory canal lies approximately 5 mm superior to the facial nerve in this region. The facial nerve is also anterior to the posterior belly of the digastric muscle and external to the styloid process.
• Alternatively, the facial nerve branches may be identified and traced back to the main trunks, although this may be more difficult depending on the ease of identifying the branching when traced retrograde.
• To perform this maneuver, the buccal branch may be found just superior to the parotid duct, or the marginal mandibular branch may be found crossing over (superficial to) the facial vessels.
• These may then be traced back to the origins of the main facial nerve trunks. Once these have been identified, the superficial lobe of the parotid gland may be removed en bloc and sent to Pathology.
• If the immediate intraoperative pathologic examination reveals that the tumor is actually high grade or more than 4 cm in greatest diameter, or lymph node metastasis is identified within the specimen, a complete total parotidectomy should be performed.
• If the facial nerve or its branches are adherent to or directly involved by the tumor, they must be sacrificed. However, a pathologic diagnosis of malignancy must be confirmed intraoperatively prior to sacrificing facial nerve branches.
• All involved local structures should be resected in continuity with the tumor. This may include skin, masseter, mandible, temporalis, zygomatic arch, or temporal bone.
• Tumors of the deep lobe are treated by total parotidectomy. Identification of the facial nerves and branches is the first and most crucial step.
• Total parotidectomy is then performed en bloc, and the fate of the facial nerve and surrounding local structures must be decided similar to superficial lobe tumors. The specimen should be sent to Pathology for immediate examination.
• Neck dissection should be performed when malignancy is detected in the lymph nodes pre- or intraoperatively.
• Other indications for functional neck dissection include tumors more than 4 cm in greatest diameter, tumors that are high grade, those that have invaded local structures, recurrent tumors when no neck dissection was performed initially, and deep lobe tumors.
• These recommendations are based on the higher likelihood of occult, clinically undetectable nodal disease present at the time of operation in patients whose tumors display the above characteristics.

RECONSTRUCTION

Section 6 of 10  

• Authors and Editors
• Introduction And Anatomy
• Diagnosis
• Pathology
• Operative Management
• Reconstruction
• Adjunctive Therapy
• Prognosis
• Surveillance
• References

Following resection of the tumor specimen, most wounds can be closed primarily. However, the presence of extension of the tumor to the overlying skin or surrounding structures may require reconstructive procedures. The overall goal following tumor excision is to restore function and achieve the best possible aesthetic result.

Options for wound closure in the presence of a skin or soft tissue deficit include skin grafting, cervicofacial flap, trapezius flap, pectoralis flap, deltopectoral flap, and microvascular free flap.

Sacrifice of the facial nerve or one of its branches also must be managed appropriately. If inadvertently severed during the operation, the facial nerve should be immediately repaired under the operating microscope. If intentionally resected with the tumor specimen, several options for reconstruction are available to the surgeon.

• The ipsilateral or contralateral greater auricular nerve may be used as an interposition graft, although sacrificing sensation to the area normally supplied by this nerve.
• Another option is to anastomose the facial nerve to the ipsilateral hypoglossal nerve. This anastomosis may be performed end to side to avoid interfering with normal hypoglossal nerve function.
• During the period of waiting for facial nerve recovery, it is important to maintain corneal protection if the innervation to the orbicularis oculi has been interrupted.
• Measures include taping the eye closed at night over ophthalmic ointment and frequent use of wetting drops during the day. Some authors recommend a moisture chamber.

Finally, if facial nerve recovery is not achieved, certain measures may be taken to improve form and function.

• A gold weight (0.8-1.2 g) may be inserted in the upper eyelid to assist with closure. Dynamic slings of temporalis muscle to the upper and lower lids and corner of the mouth or masseter sling to the mouth have proven very successful in the reconstruction of these patients. Static slings also have been used and include fascia lata, tendon, and mitek anchors.
• Following parotidectomy, some patients develop gustatory sweating or Frey syndrome. This denotes an aberrant connection of regenerating parasympathetic salivary fibers to the sweat glands in the overlying skin flap.
• Treatment of this condition has included irradiation, atropinelike creams, division of the auriculotemporal nerve (sensory), and division of the glossopharyngeal nerve (parasympathetic).
• Others advocate the insertion of synthetic materials (alloderm), fascial grafts, or vascularized tissue flaps between the parotid bed and overlying skin flap.

ADJUNCTIVE THERAPY

Section 7 of 10  

• Authors and Editors
• Introduction And Anatomy
• Diagnosis
• Pathology
• Operative Management
• Reconstruction
• Adjunctive Therapy
• Prognosis
• Surveillance
• References

No chemotherapy has proven effective, and, presently, immunotherapy is in the clinical trial phase. Therefore, radiation therapy is the cornerstone of adjunctive therapy.

Indications for radiation include tumors more than 4 cm in greatest diameter, those of high grade, tumor invasion of local structures, lymphatic invasion, neural invasion, vascular invasion, tumor present very close to a nerve that was spared, tumors originating in or extending to the deep lobe, recurrent tumors following re-resection, positive margins on final pathology, and lymph node involvement.

Essentially, radiation is indicated for all but small, low-grade tumors with no evidence of local invasion or nodal/distant spread.

PROGNOSIS

Section 8 of 10  

• Authors and Editors
• Introduction And Anatomy
• Diagnosis
• Pathology
• Operative Management
• Reconstruction
• Adjunctive Therapy
• Prognosis
• Surveillance
• References

The major determinants of survival are histology and clinical stage. Poor prognostic factors include high grade, neural involvement, locally advanced disease, advanced age, associated pain, regional or distant metastasis, and accumulation of p53 or c-erbB2 oncoproteins.

Although statements regarding survival are difficult to make because of the large variety of histologic types, 20% of all patients will develop distant metastases.

Overall 5-year survival for all stages and histologic types is approximately 62%. The overall 5-year survival for recurrent disease is approximately 37%.

SURVEILLANCE

Section 9 of 10  

• Authors and Editors
• Introduction And Anatomy
• Diagnosis
• Pathology
• Operative Management
• Reconstruction
• Adjunctive Therapy
• Prognosis
• Surveillance
• References

Surveillance must continue indefinitely, as local recurrence or distant metastases may become apparent many years after the initial treatment.

The patient should undergo a thorough physical examination every 3 months for 2 years, every 6 months for another 3 years, then yearly thereafter. Liver function tests and chest radiograph should be obtained yearly.

REFERENCES

Section 10 of 10

• Authors and Editors
• Introduction And Anatomy
• Diagnosis
• Pathology
• Operative Management
• Reconstruction
• Adjunctive Therapy
• Prognosis
• Surveillance
• References

• Eneroth CM, Franzen S, Zajicek J. Aspiration biopsy of salivary gland tumors. A critical review of 910 biopsies. Acta Cytol. Nov-Dec 1967;11(6):470-2. [Medline].
• Frankenthaler RA, Luna MA, Lee SS, et al. Prognostic variables in parotid gland cancer. Arch Otolaryngol Head Neck Surg. Nov 1991;117(11):1251-6. [Medline].
• Illes RW, Brian MB. A review of the tumors of the salivary gland. Surg Gynecol Obstet. Oct 1986;DA - 19861107(4):399-404. [Medline].
• Johns ME. Parotid cancer: a rational basis for treatment. Head Neck Surg. Nov-Dec 1980;3(2):132-41. [Medline].
• Laforga JB. Mucoepidermoid carcinoma of the parotid gland [letter]. Acta Cytol. May-Jun 1999;43(3):515-7. [Medline].
• O''Brien CJ, Soong SJ, Herrera GA, et al. Malignant salivary tumors--analysis of prognostic factors and survival. Head Neck Surg. Nov-Dec 1986;9(2):82-92. [Medline].
• Pinkston JA, Cole P. Incidence rates of salivary gland tumors: results from a population-based study. Otolaryngol Head Neck Surg. Jun 1999;120(6):834-40. [Medline].
• Rice DH, Becker T. Magnetic resonance imaging of the salivary glands. A comparison with computed tomographic scanning. Arch Otolaryngol Head Neck Surg. Jan 1987;113(1):78-80. [Medline].
• Shikhani A, Samara M, Allam C, et al. Primary lymphoma in the salivary glands: report of five cases and review of the literature. Laryngoscope. Dec 1987;97(12):1438-42. [Medline].
• Skolnik EM, Friedman M, Becker S, et al. Tumors of the major salivary glands. Laryngoscope. Jun 1977;87(6):843-61. [Medline].
• Snyderman NL, Johnson JT. Salivary gland tumors. Diagnostic characteristics of the common types. Postgrad Med. Oct 1987;82(5):105-8, 110-2. [Medline].
• Spiro RH. Salivary neoplasms: overview of a 35-year experience with 2,807 patients. Head Neck Surg. Jan-Feb 1986;8(3):177-84. [Medline].
• Stafford ND, Wilde A. Parotid cancer. Surg Oncol. Dec 1997;6(4):209-13. [Medline].
• Suzuki M, Ichimiya I, Matsushita F, Mogi G. Histological features and prognosis of patients with mucoepidermoid carcinoma of the parotid gland. J Laryngol Otol. Oct 1998;112(10):944-7. [Medline].

Article Last Updated: Mar 10, 2006