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Salivary Glands
process is similar for all of the major salivary gland embryogenesis.2 During early gestation, the parotid ductules begin to grow around the facial nerve and its branches. This is of great clinical and surgical significance, because the facial nerve may be compressed or invaded by parotid gland lesions, or its branches may be injured during parotid gland surgery.3
Anatomy and Physiology ------------------------------------------------------------------------------------------------------------------------------------------------
CHAPTER 56
Salivary Glands Douglas Sidell and Nina L. Shapiro
Salivary gland disorders are rare in children. They often present as a painful or, less commonly, a painless swelling in the affected gland. Disease processes may be of infectious, inflammatory, systemic, autoimmune, congenital, neoplastic, or traumatic origin.1 Treatment is guided by the medical or surgical nature of the specific disease process.
Classification ------------------------------------------------------------------------------------------------------------------------------------------------
Salivary glands may be divided into major and minor categories. The former category includes the parotid, submandibular, and sublingual glands, all of which are paired structures with their own well-defined anatomy, including blood supply and ductal drainage. Their function is augmented and facilitated by the minor salivary glands, which include the mucus-secreting tissues in the buccal mucosa, palate, mucosal surfaces of the lips, and floor of the mouth.
Embryology ------------------------------------------------------------------------------------------------------------------------------------------------
In the sixth week of gestation, solid epithelial buds of ectoderm from the developing mouth invaginate into the surrounding mesenchyme. A groove from this invagination develops into a tunnel, which subsequently forms branches of salivary ductal tissue. The mesenchymal tissue forms the capsule and connective tissue of the salivary glands. This
The parotid gland is located in the space between the external auditory canal and the mandible. Its main duct (Stensen duct) crosses the masseter muscle and opens in the buccal mucosa at the level of the second maxillary molar. The deep lobe of the parotid gland lies medial to the facial nerve branches and the mandible. Deep lobe parotid gland masses may extend to the parapharyngeal space and present as intraoral growths. The parotid gland is the only salivary gland containing lymph nodes, which may become apparent during certain pathologic processes, such as atypical mycobacterial adenitis (see Chapter 57). Accessory parotid tissue is present in some children and in approximately 20% of adults. It can occur superficial to the masseter and is often mistaken for a neoplasm.4 The submandibular gland is located in the submandibular triangle of the neck. The main submandibular duct (Wharton duct) exits the gland at a right angle and enters the mouth just lateral to the midline lingual frenulum. The sublingual gland is located at the lateral aspect of the floor of the mouth.1 The salivary glands serve to lubricate the mouth for hygiene, speech, and deglutition; to moisten food for taste and mastication; and to initiate early starch digestion with a-amylase.1 These processes may be initiated by various stimuli, including cerebral, visual, olfactory, or gustatory.
Pathology ------------------------------------------------------------------------------------------------------------------------------------------------
The majority of salivary masses in children are congenital vascular lesions, with hemangiomas seen in 50% to 60% of salivary gland masses and lymphatic malformations in approximately 25%.5 Acquired lesions are of inflammatory, infectious, autoimmune, traumatic, or neoplastic origin. Salivary gland swelling is characteristic of nearly all glandular pathologic processes, and may be accompanied by pain, tenderness, or abnormal ductal discharge.4 Advanced stages of disease may lead to cranial nerve involvement with resultant paresis or paralysis.
Diagnosis ------------------------------------------------------------------------------------------------------------------------------------------------
HISTORY A careful history should focus on the duration of the lesion, its bilateral or unilateral presentation, and whether there is any symptom fluctuation associated with eating. A complete medical history is essential, because the salivary glands may be involved in several systemic conditions.
PHYSICAL EXAMINATION The physical examination should include careful inspection of the overlying skin, both local and distant, to evaluate for any cutaneous hemangiomas, as well as of the intraoral mucosa to 729
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evaluate for intraoral extension of the mass. Longitudinal duct massage will assess for duct obstruction or purulent material in the saliva. Benign salivary lesions tend to be mobile, soft, and spongy, whereas malignant and infectious lesions are more often fixed and firm on palpation.
DIAGNOSTIC IMAGING Plain radiographs of the salivary glands are helpful in detecting salivary duct calculi or diffuse glandular calcification.1 Sialography is useful in identifying strictures, sialectasis, calculi, or saccular dilatation (Fig. 56-1).6 High-resolution ultrasonography is a useful, noninvasive technique in the diagnosis of sialectasis and salivary gland calculi.7 The addition of color-flow Doppler imaging can provide accurate information regarding the consistency of the lesion and its vascular pattern (Fig. 56-2).8 Computed Tomography Computed tomography (CT) is an excellent diagnostic modality for assessing both the pathology and anatomy of the salivary glands. It can aid in distinguishing intrinsic or extrinsic lesions. Use of an intravenous contrast agent can help detect an abscess or delineate the vascularity of congenital and acquired vascular lesions.1 These features help in both medical and surgical planning.9,10 Magnetic Resonance Imaging Magnetic resonance imaging (MRI) provides the best soft tissue detail of the salivary glands, and it is the only imaging technique that can delineate the facial nerve anatomy within the parotid glands. Signal intensity variations (T1- and T2weighted images) provide additional valuable information regarding the nature of the mass.11,12
FIGURE 56-2 Doppler ultrasound study shows vascular pooling in a parotid hemangioma.
BIOPSY Fine-needle aspiration (FNA) biopsy is an excellent tool in the diagnostic evaluation of salivary gland masses.13,14 The overall diagnostic accuracy is 84%, with a sensitivity and specificity approaching 92% for parotid lesions.15–17 Obtaining an adequate needle biopsy specimen may preclude the necessity for surgical therapy or aid in surgical planning. Understandably, the accuracy and dependability of FNA rely heavily on the expertise of the cytopathologist and may vary based on institution or clinical setting.13 For deeper salivary gland tumors, fine-needle aspiration may be performed under image guidance. Open excisional biopsy is the definitive tool for investigation and may be curative. If the size and location of the lesion are favorable, the entire tumor may be resected intact with a clear surrounding cuff of normal tissue. The diagnosis of Sjo¨gren syndrome may be obtained by incisional biopsy of the minor salivary glands of the labial mucosa, or, alternatively, of the parotid gland.18
SIALENDOSCOPY
FIGURE 56-1 Sialogram shows saccular sialolithiasis of the parotid gland.
Sialendoscopy involves semirigid endoscopy and microinstrumentation to evaluate and treat certain disorders of the parotid and submandibular glands. Although relatively new, this technique is increasing in popularity and has been demonstrated to effectively classify and treat ductal lesions, such as stricture and calculi. Sialendoscopy has been reported to produce a greater sensitivity in detecting salivary calculi than conventional radiography, MRI, or ultrasonography. Duct marsupialization and intraductal calculi retrieval have been demonstrated, allowing for the early treatment of some lesions without the requirement for open surgery.19,20
CHAPTER 56
Inflammatory Disease
SALIVARY GLANDS
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CHRONIC SIALADENITIS
------------------------------------------------------------------------------------------------------------------------------------------------
VIRAL SIALADENITIS Acute inflammation of the salivary glands may be viral in up to 85% of cases, and the majority of viral sialadenitis involves the parotid glands. Viral infections are characterized by a benign self-limiting course over 2 to 3 weeks. Antipyretics, analgesics, and anti-inflammatory agents may be given for relief of symptoms. Causative organisms include coxsackievirus A and echovirus. Before the nearly universal implementation of the mumps vaccine in 1967, mumps virus (paramyxovirus) was the most common cause of acute parotid inflammation in children.21–24 Other potential causes include cytomegalovirus (CMV), which is most commonly seen as a component of disseminated CMV infection in infants and young children,25 and Epstein-Barr virus (EBV), which in healthy children is associated with infectious mononucleosis and in chronically ill children may be associated with human immunodeficiency virus (HIV) infection.26,27
BACTERIAL SUPPURATIVE SIALADENITIS Acute suppurative sialadenitis most often presents as rapidly developing pain, swelling, and occasional ductal discharge, with associated fever and poor oral intake. It is primarily seen in the parotid glands and less commonly in the submandibular or sublingual glands. The causative organisms are usually Staphylococcus aureus and Streptococcus viridans.28 Acute sialadenitis often occurs in dehydrated patients because of decrease in salivary flow and dry oral mucosa.29 Most cases will respond to antistaphylococcal antibiotics, with careful attention to hydration, oral hygiene with mouthwashes, warm local compresses, and sialogogues, such as sour lemon drop candies, to stimulate salivary flow. Rarely, despite treatment, the infected tissue will coalesce to form an abscess. Treatment of a salivary gland abscess includes intravenous antibiotics and surgical drainage.30 If an abscess develops in the parotid gland, fascial incisions parallel to the course of the facial nerve are made to drain the abscess. If the facial nerve is paretic preoperatively, abscess drainage will usually facilitate resolution of nerve function.1
A
Chronic sialadenitis is the most common cause of inflammatory salivary gland disease in children and may lead to structural changes in the gland and acinar destruction (Fig. 56-3). There are obstructive and nonobstructive causes of this condition. Obstruction is caused by ductal stenosis, which may be congenital, caused by a stone, or result from chewing or biting the ductal opening. In such cases, the duct should be probed and stented for continuous drainage. Nonobstructive chronic sialadenitis may occur in conjunction with metabolic disorders, such as Sjo¨gren syndrome, or chronic granulomatous disease, such as sarcoidosis, tuberculosis, or atypical mycobacterial disease. The treatment of obstructive sialadenitis is initially conservative, with warm compresses and anti-inflammatory medications. Ductal dilatation or marsupialization may be necessary for recalcitrant disease. Gland excision is rarely required. Sialolithiasis (salivary gland or duct calculi) is rare in children and occurs in the submandibular gland in 80% of cases. When the stone is located at the distal salivary duct, it may be excised by a simple incision at the ductal orifice. Temporary stent placement may be necessary. Rarely, a large calculus will be located in the proximal salivary duct or salivary gland parenchyma and may require complete gland excision with the stone-containing duct.
Cystic Disease ------------------------------------------------------------------------------------------------------------------------------------------------
Cystic disease may be acquired, congenital, or traumatic. Congenital cystic disease may occur in the salivary glands, but it is not of salivary gland origin. Work type I and type II first branchial cleft cysts may present as parotid gland masses, and depending on the orientation of the tract, may have accompanying otorrhea.31,32 Congenital lymphatic malformations may also present in the parotid, submandibular, or sublingual glands. Large, bilateral intraparotid lymphoepithelial cysts are characteristic of HIV infection.1 Small mucous retention cysts may present in the minor salivary glands of the labial or buccal mucosa; these cysts usually result from single or
B
FIGURE 56-3 A, Sialogram of patient with history of recurrent parotid swelling. Note normal ductal system with early diffuse punctate sialectasis. B, Parotid gland swelling between acute attacks of inflammation.
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FIGURE 56-4 Floor of mouth ranula with posterosuperior lingual elevation.
repeated local trauma to the minor salivary glands and may lead to recurrent local mucosal swellings. If they do not resolve spontaneously, they will require complete excision. Local drainage or marsupialization will result in recurrence.
RANULA A ranula is a mucus extravasation cyst of the sublingual gland. Initial presentation is a bluish, cystic mass at the floor of mouth, which may lead to lingual elevation or difficulty with deglutition. They may extend to the neck through the mylohyoid (plunging ranula) (Fig. 56-4). Surgical management is controversial and ranges from simple transoral marsupialization to combination transoral-transcervical approaches.33,34 Despite controversy, recurrence rates as high as 67% have been described with marsupialization alone. Recent evidence, derived from the largest review to date, suggests that the excision of the ipsilateral sublingual gland produces the lowest incidence of recurrence.35 During sublingual gland excision, care must be taken to avoid Wharton duct injury, and it can be avoided by placing a lacrimal probe in the duct intraoperatively. The lingual nerve must also be meticulously dissected just deep to the sublingual gland.
Neoplasms ------------------------------------------------------------------------------------------------------------------------------------------------
Salivary gland neoplasms are extremely rare in children and comprise less than 1% of all pediatric neoplasms.5,28,36,37 Less than 5% of salivary gland neoplasms occur in patients younger than 16 years of age.38,39 However, when present, a pediatric salivary tumor must be assessed to rule out malignancy.40–42 In the pediatric population, greater than 90% of salivary neoplasms occur in the parotid gland.43 Caution should be exercised when evaluating adolescents, because imaging characteristics change over time as the gland is replaced with fat. Occasionally, this can cause benign disease to be mistaken for an infiltrative tumor on CT.4
BENIGN NEOPLASMS AND MALFORMATIONS Benign neoplasms account for 60% of salivary tumors in children and are most commonly vascular in origin.5 Vascular lesions include hemangiomas and lymphatic malformations, which are both congenital in origin (Fig. 56-5).
FIGURE 56-5 Vascular malformation of the parotid gland, showing large, irregular vascular spaces. (Hematoxylin-eosin stain, 50.)
Hemangiomas Hemangiomas are one of the most common salivary (primarily intraparotid) neoplasms in children, with infantile hemangiomas comprising greater than 90% of all salivary lesions in children less than 1 year of age.4 Hemangiomas usually present in infancy as a soft, nontender parotid swelling, with or without associated pigmented cutaneous lesions.44 Diagnosis is usually confirmed with ultrasonography, which demonstrates a lobulated, hypervascular mass, with arterial and venous signals visible on color-flow Doppler.4,45 MRI may also be useful but is rarely required. Parotid hemangiomas often resolve spontaneously and do not require treatment. If they are rapidly growing or are causing functional impairments, such as facial nerve weakness, external auditory canal obstruction, or cutaneous breakdown, systemic therapy such as corticosteroids, propranolol, or interferon alfa-2a or alfa-2b are viable options to inhibit vascular growth and promote involution of the tumor.46–49 Lymphatic Malformations Lymphatic malformations are less common than hemangiomas. They do not undergo spontaneous involution, are usually present at or soon after birth, and grow with the growth of the child.44 They are not true salivary lesions, but they are commonly seen in the submandibular and parotid region in infants and young children.50 Lymphatic malformations are susceptible to infection, with potential for cellulitis, intralesional bleeding, abscess formation, or lymphangiomatous extension to the floor of mouth or trachea with airway compromise. Treatment modalities have been an area of much investigation. Surgical resection must be complete to obviate recurrence. This is often difficult, because of the fragility of the tumor lining, its infiltrative nature, and its proximity to major vessels and branches of the facial nerve.51,52 In an effort to avoid surgical morbidity, success with intralesional sclerotherapy has been demonstrated, resulting in reduction in tumor size and minimal scarring or recurrence.53 Pleomorphic Adenoma Pleomorphic adenomas (benign mixed tumors) are the most common nonvascular benign salivary tumors in children (Fig. 56-6).42,54 They present as firm, rubbery masses, most often in the parotid gland, with an average age at presentation of 9.5 years within the pediatric population.54,55 The tumor
CHAPTER 56
SALIVARY GLANDS
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involving the submandibular or minor salivary glands, concomitant neck dissection and adjuvant radiation therapy is recommended by many institutions.36,64,65 Acinic Cell Carcinoma Acinic cell carcinomas present in a similar fashion as mucoepidermoid carcinomas. They tend to be low grade, and treatment is similar to that of mucoepidermoid carcinoma (Fig. 56-7). Adenoid Cystic Carcinoma Adenoid cystic carcinoma is a rare, high-grade salivary gland tumor. Perineural invasion may result in cranial nerve deficits. There is a high incidence of regional nodal metastases, as well as distant metastases to the lungs, liver, and bone. Treatment includes wide surgical resection, neck dissection, and adjuvant radiation therapy.61 FIGURE 56-6 Pleomorphic adenoma (mixed tumor) of the parotid gland. Epithelial areas are mixed with myxomatoid and chondroid stroma. (Hematoxylin-eosin stain, 50.)
presents as a painless, slowly growing mass and is rarely infiltrative.56 They have variable echogenicity on imaging, with increased heterogenicity seen in larger lesions secondary to necrosis or cystic changes.4 Treatment of superficial lobe tumors includes superficial parotidectomy with facial nerve dissection and preservation. Recurrence rates have been reported to be up to 40%; so, long-term follow-up is recommended.57,58 Simple excisional biopsy should be avoided, because it is associated with a higher recurrence rate. Rarely, recurrent pleomorphic adenomas may undergo malignant degeneration.59
Rhabdomyosarcoma Rhabdomyosarcoma may present as a parotid mass. Histologic variants include undifferentiated and embryonal types (Fig. 56-8). Treatment and outcomes depend on tumor stage and may include wide local surgical resection with radiation and chemotherapy.
Monomorphic Adenomas Monomorphic adenomas are rare in children. Histologically, they may resemble adenoid cystic carcinoma, a highly aggressive malignant salivary tumor.60 Treatment includes complete surgical resection and close long-term follow-up. Papillary Cystadenoma Lymphomatosum (Warthin Tumor) These tumors are most commonly seen in men and are often bilateral parotid lesions. They may rarely present as benign parotid tumors in children.1 Treatment is similar to that for pleomorphic adenomas.
FIGURE 56-7 Acinic cell carcinoma of the parotid gland showing invasive proliferation. (Hematoxylin-eosin stain, 100.)
MALIGNANT NEOPLASMS Malignant salivary neoplasms are rare in children. When present, they are often low-grade lesions, located most commonly in the parotid gland, and have a female preponderance.54 Diagnostic evaluation should include CT or MRI and fineneedle aspiration biopsy. Treatment is surgical, with complete tumor excision with clear margins. Invasive malignancies may require sacrifice of the facial nerve branches. Postoperative radiation therapy is recommended for high-grade lesions.61,62 Mucoepidermoid Carcinoma Mucoepidermoid carcinoma is the most common pediatric salivary malignancy and is most commonly low grade and located in the parotid gland. Surgery is usually curative.39,63 For high-grade mucoepidermoid carcinomas, or those
FIGURE 56-8 Rhabdomyosarcoma of the parotid gland showing spindle cell sarcoma with myogenous differentiation. (Hematoxylin-eosin stain, 100.)
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Surgical Considerations ------------------------------------------------------------------------------------------------------------------------------------------------
PAROTID GLAND An S-shaped incision is made, beginning in the preauricular crease and extending in a curvilinear fashion to the postauricular region, followed by an inferior extension to 2 fingerbreadths below the angle of the mandible (Fig. 56-9). Skin
flaps are elevated, and the greater auricular nerve and posterior facial vein will be identified and may need to be sacrificed to expose the posterior border of the parotid gland. Blunt dissection along the tragal pointer and mastoid process, following the posterior belly of the digastric muscle, will allow visualization of the main trunk of the facial nerve as it emerges from the stylomastoid foramen. Meticulous dissection along the facial nerve branches in an anterior direction will elevate
Parotid gland sup. lobe Sup. temporal v. and a.
FACIAL NERVE Mastoid process Gr. auricular ns. Parotid gland deep lobe
Zygoma
Pterygoid fossa Cartilage of external auditory canal
Masseter m. FACIAL NERVE
Mastoid process
FIGURE 56-9 Technique for parotidectomy.
CHAPTER 56
the superficial lobe of the parotid gland. Careful blunt dissection, with use of the bipolar cautery and facial nerve monitor, will maximize excellent surgical results with minimal morbidity.64,67
SUBMANDIBULAR GLAND For submandibular gland resection, a horizontal skin incision is made in a natural skin crease approximately two fingerbreadths inferior to the body of the mandible. The dissection plane is carried to the investing fascia of the submandibular gland. Exposure should reveal the mylohyoid muscle anteriorly, the sternocleidomastoid muscle posteriorly, and the digastric muscle inferiorly. Identification and division of the anterior facial vein, just deep to this fascia, will facilitate protection of the facial nerve. Anterior retraction of the mylohyoid muscle and downward retraction on the submandibular gland will enable identification of the lingual nerve and Wharton duct. Division of the duct will free the lingual nerve from the gland and allow complete blunt dissection of the gland.66
SALIVARY GLANDS
735
Conclusion ------------------------------------------------------------------------------------------------------------------------------------------------
Although salivary gland disorders are rare in childhood, knowledge of the anatomy of the major salivary glands and understanding of both systemic and neoplastic physiology is critical. Neoplasms of the salivary glands are very rare in children and are commonly benign.31,68 Evaluation and management should be tailored to the specific entity. A multitude of diagnostic tools are available and may include radiologic or pathologic studies. Inflammatory and infectious disorders are often treated medically, whereas neoplastic disorders require surgical intervention. Patients and families must be counseled regarding potential short-term and long-term complications of facial nerve injury. Despite the rigorous demands of parotid and submandibular gland surgery, in experienced hands, with adequate monitoring and meticulous dissection and hemostasis, surgical results are excellent.67 The complete reference list is available online at www. expertconsult.com.
Anatomy and Physiology ------------------------------------------------------------------------------------------------------------------------------------------------
CHAPTER 56
Salivary Glands Douglas Sidell and Nina L. Shapiro
Salivary gland disorders are rare in children. They often present as a painful or, less commonly, a painless swelling in the affected gland. Disease processes may be of infectious, inflammatory, systemic, autoimmune, congenital, neoplastic, or traumatic origin.1 Treatment is guided by the medical or surgical nature of the specific disease process.
Classification ------------------------------------------------------------------------------------------------------------------------------------------------
Salivary glands may be divided into major and minor categories. The former category includes the parotid, submandibular, and sublingual glands, all of which are paired structures with their own well-defined anatomy, including blood supply and ductal drainage. Their function is augmented and facilitated by the minor salivary glands, which include the mucus-secreting tissues in the buccal mucosa, palate, mucosal surfaces of the lips, and floor of the mouth.
Embryology ------------------------------------------------------------------------------------------------------------------------------------------------
In the sixth week of gestation, solid epithelial buds of ectoderm from the developing mouth invaginate into the surrounding mesenchyme. A groove from this invagination develops into a tunnel, which subsequently forms branches of salivary ductal tissue. The mesenchymal tissue forms the capsule and connective tissue of the salivary glands. This
The parotid gland is located in the space between the external auditory canal and the mandible. Its main duct (Stensen duct) crosses the masseter muscle and opens in the buccal mucosa at the level of the second maxillary molar. The deep lobe of the parotid gland lies medial to the facial nerve branches and the mandible. Deep lobe parotid gland masses may extend to the parapharyngeal space and present as intraoral growths. The parotid gland is the only salivary gland containing lymph nodes, which may become apparent during certain pathologic processes, such as atypical mycobacterial adenitis (see Chapter 57). Accessory parotid tissue is present in some children and in approximately 20% of adults. It can occur superficial to the masseter and is often mistaken for a neoplasm.4 The submandibular gland is located in the submandibular triangle of the neck. The main submandibular duct (Wharton duct) exits the gland at a right angle and enters the mouth just lateral to the midline lingual frenulum. The sublingual gland is located at the lateral aspect of the floor of the mouth.1 The salivary glands serve to lubricate the mouth for hygiene, speech, and deglutition; to moisten food for taste and mastication; and to initiate early starch digestion with a-amylase.1 These processes may be initiated by various stimuli, including cerebral, visual, olfactory, or gustatory.
Pathology ------------------------------------------------------------------------------------------------------------------------------------------------
The majority of salivary masses in children are congenital vascular lesions, with hemangiomas seen in 50% to 60% of salivary gland masses and lymphatic malformations in approximately 25%.5 Acquired lesions are of inflammatory, infectious, autoimmune, traumatic, or neoplastic origin. Salivary gland swelling is characteristic of nearly all glandular pathologic processes, and may be accompanied by pain, tenderness, or abnormal ductal discharge.4 Advanced stages of disease may lead to cranial nerve involvement with resultant paresis or paralysis.
Diagnosis ------------------------------------------------------------------------------------------------------------------------------------------------
HISTORY A careful history should focus on the duration of the lesion, its bilateral or unilateral presentation, and whether there is any symptom fluctuation associated with eating. A complete medical history is essential, because the salivary glands may be involved in several systemic conditions.
PHYSICAL EXAMINATION The physical examination should include careful inspection of the overlying skin, both local and distant, to evaluate for any cutaneous hemangiomas, as well as of the intraoral mucosa to 729
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evaluate for intraoral extension of the mass. Longitudinal duct massage will assess for duct obstruction or purulent material in the saliva. Benign salivary lesions tend to be mobile, soft, and spongy, whereas malignant and infectious lesions are more often fixed and firm on palpation.
DIAGNOSTIC IMAGING Plain radiographs of the salivary glands are helpful in detecting salivary duct calculi or diffuse glandular calcification.1 Sialography is useful in identifying strictures, sialectasis, calculi, or saccular dilatation (Fig. 56-1).6 High-resolution ultrasonography is a useful, noninvasive technique in the diagnosis of sialectasis and salivary gland calculi.7 The addition of color-flow Doppler imaging can provide accurate information regarding the consistency of the lesion and its vascular pattern (Fig. 56-2).8 Computed Tomography Computed tomography (CT) is an excellent diagnostic modality for assessing both the pathology and anatomy of the salivary glands. It can aid in distinguishing intrinsic or extrinsic lesions. Use of an intravenous contrast agent can help detect an abscess or delineate the vascularity of congenital and acquired vascular lesions.1 These features help in both medical and surgical planning.9,10 Magnetic Resonance Imaging Magnetic resonance imaging (MRI) provides the best soft tissue detail of the salivary glands, and it is the only imaging technique that can delineate the facial nerve anatomy within the parotid glands. Signal intensity variations (T1- and T2weighted images) provide additional valuable information regarding the nature of the mass.11,12
FIGURE 56-2 Doppler ultrasound study shows vascular pooling in a parotid hemangioma.
BIOPSY Fine-needle aspiration (FNA) biopsy is an excellent tool in the diagnostic evaluation of salivary gland masses.13,14 The overall diagnostic accuracy is 84%, with a sensitivity and specificity approaching 92% for parotid lesions.15–17 Obtaining an adequate needle biopsy specimen may preclude the necessity for surgical therapy or aid in surgical planning. Understandably, the accuracy and dependability of FNA rely heavily on the expertise of the cytopathologist and may vary based on institution or clinical setting.13 For deeper salivary gland tumors, fine-needle aspiration may be performed under image guidance. Open excisional biopsy is the definitive tool for investigation and may be curative. If the size and location of the lesion are favorable, the entire tumor may be resected intact with a clear surrounding cuff of normal tissue. The diagnosis of Sjo¨gren syndrome may be obtained by incisional biopsy of the minor salivary glands of the labial mucosa, or, alternatively, of the parotid gland.18
SIALENDOSCOPY
FIGURE 56-1 Sialogram shows saccular sialolithiasis of the parotid gland.
Sialendoscopy involves semirigid endoscopy and microinstrumentation to evaluate and treat certain disorders of the parotid and submandibular glands. Although relatively new, this technique is increasing in popularity and has been demonstrated to effectively classify and treat ductal lesions, such as stricture and calculi. Sialendoscopy has been reported to produce a greater sensitivity in detecting salivary calculi than conventional radiography, MRI, or ultrasonography. Duct marsupialization and intraductal calculi retrieval have been demonstrated, allowing for the early treatment of some lesions without the requirement for open surgery.19,20
CHAPTER 56
Inflammatory Disease
SALIVARY GLANDS
731
CHRONIC SIALADENITIS
------------------------------------------------------------------------------------------------------------------------------------------------
VIRAL SIALADENITIS Acute inflammation of the salivary glands may be viral in up to 85% of cases, and the majority of viral sialadenitis involves the parotid glands. Viral infections are characterized by a benign self-limiting course over 2 to 3 weeks. Antipyretics, analgesics, and anti-inflammatory agents may be given for relief of symptoms. Causative organisms include coxsackievirus A and echovirus. Before the nearly universal implementation of the mumps vaccine in 1967, mumps virus (paramyxovirus) was the most common cause of acute parotid inflammation in children.21–24 Other potential causes include cytomegalovirus (CMV), which is most commonly seen as a component of disseminated CMV infection in infants and young children,25 and Epstein-Barr virus (EBV), which in healthy children is associated with infectious mononucleosis and in chronically ill children may be associated with human immunodeficiency virus (HIV) infection.26,27
BACTERIAL SUPPURATIVE SIALADENITIS Acute suppurative sialadenitis most often presents as rapidly developing pain, swelling, and occasional ductal discharge, with associated fever and poor oral intake. It is primarily seen in the parotid glands and less commonly in the submandibular or sublingual glands. The causative organisms are usually Staphylococcus aureus and Streptococcus viridans.28 Acute sialadenitis often occurs in dehydrated patients because of decrease in salivary flow and dry oral mucosa.29 Most cases will respond to antistaphylococcal antibiotics, with careful attention to hydration, oral hygiene with mouthwashes, warm local compresses, and sialogogues, such as sour lemon drop candies, to stimulate salivary flow. Rarely, despite treatment, the infected tissue will coalesce to form an abscess. Treatment of a salivary gland abscess includes intravenous antibiotics and surgical drainage.30 If an abscess develops in the parotid gland, fascial incisions parallel to the course of the facial nerve are made to drain the abscess. If the facial nerve is paretic preoperatively, abscess drainage will usually facilitate resolution of nerve function.1
A
Chronic sialadenitis is the most common cause of inflammatory salivary gland disease in children and may lead to structural changes in the gland and acinar destruction (Fig. 56-3). There are obstructive and nonobstructive causes of this condition. Obstruction is caused by ductal stenosis, which may be congenital, caused by a stone, or result from chewing or biting the ductal opening. In such cases, the duct should be probed and stented for continuous drainage. Nonobstructive chronic sialadenitis may occur in conjunction with metabolic disorders, such as Sjo¨gren syndrome, or chronic granulomatous disease, such as sarcoidosis, tuberculosis, or atypical mycobacterial disease. The treatment of obstructive sialadenitis is initially conservative, with warm compresses and anti-inflammatory medications. Ductal dilatation or marsupialization may be necessary for recalcitrant disease. Gland excision is rarely required. Sialolithiasis (salivary gland or duct calculi) is rare in children and occurs in the submandibular gland in 80% of cases. When the stone is located at the distal salivary duct, it may be excised by a simple incision at the ductal orifice. Temporary stent placement may be necessary. Rarely, a large calculus will be located in the proximal salivary duct or salivary gland parenchyma and may require complete gland excision with the stone-containing duct.
Cystic Disease ------------------------------------------------------------------------------------------------------------------------------------------------
Cystic disease may be acquired, congenital, or traumatic. Congenital cystic disease may occur in the salivary glands, but it is not of salivary gland origin. Work type I and type II first branchial cleft cysts may present as parotid gland masses, and depending on the orientation of the tract, may have accompanying otorrhea.31,32 Congenital lymphatic malformations may also present in the parotid, submandibular, or sublingual glands. Large, bilateral intraparotid lymphoepithelial cysts are characteristic of HIV infection.1 Small mucous retention cysts may present in the minor salivary glands of the labial or buccal mucosa; these cysts usually result from single or
B
FIGURE 56-3 A, Sialogram of patient with history of recurrent parotid swelling. Note normal ductal system with early diffuse punctate sialectasis. B, Parotid gland swelling between acute attacks of inflammation.
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FIGURE 56-4 Floor of mouth ranula with posterosuperior lingual elevation.
repeated local trauma to the minor salivary glands and may lead to recurrent local mucosal swellings. If they do not resolve spontaneously, they will require complete excision. Local drainage or marsupialization will result in recurrence.
RANULA A ranula is a mucus extravasation cyst of the sublingual gland. Initial presentation is a bluish, cystic mass at the floor of mouth, which may lead to lingual elevation or difficulty with deglutition. They may extend to the neck through the mylohyoid (plunging ranula) (Fig. 56-4). Surgical management is controversial and ranges from simple transoral marsupialization to combination transoral-transcervical approaches.33,34 Despite controversy, recurrence rates as high as 67% have been described with marsupialization alone. Recent evidence, derived from the largest review to date, suggests that the excision of the ipsilateral sublingual gland produces the lowest incidence of recurrence.35 During sublingual gland excision, care must be taken to avoid Wharton duct injury, and it can be avoided by placing a lacrimal probe in the duct intraoperatively. The lingual nerve must also be meticulously dissected just deep to the sublingual gland.
Neoplasms ------------------------------------------------------------------------------------------------------------------------------------------------
Salivary gland neoplasms are extremely rare in children and comprise less than 1% of all pediatric neoplasms.5,28,36,37 Less than 5% of salivary gland neoplasms occur in patients younger than 16 years of age.38,39 However, when present, a pediatric salivary tumor must be assessed to rule out malignancy.40–42 In the pediatric population, greater than 90% of salivary neoplasms occur in the parotid gland.43 Caution should be exercised when evaluating adolescents, because imaging characteristics change over time as the gland is replaced with fat. Occasionally, this can cause benign disease to be mistaken for an infiltrative tumor on CT.4
BENIGN NEOPLASMS AND MALFORMATIONS Benign neoplasms account for 60% of salivary tumors in children and are most commonly vascular in origin.5 Vascular lesions include hemangiomas and lymphatic malformations, which are both congenital in origin (Fig. 56-5).
FIGURE 56-5 Vascular malformation of the parotid gland, showing large, irregular vascular spaces. (Hematoxylin-eosin stain, 50.)
Hemangiomas Hemangiomas are one of the most common salivary (primarily intraparotid) neoplasms in children, with infantile hemangiomas comprising greater than 90% of all salivary lesions in children less than 1 year of age.4 Hemangiomas usually present in infancy as a soft, nontender parotid swelling, with or without associated pigmented cutaneous lesions.44 Diagnosis is usually confirmed with ultrasonography, which demonstrates a lobulated, hypervascular mass, with arterial and venous signals visible on color-flow Doppler.4,45 MRI may also be useful but is rarely required. Parotid hemangiomas often resolve spontaneously and do not require treatment. If they are rapidly growing or are causing functional impairments, such as facial nerve weakness, external auditory canal obstruction, or cutaneous breakdown, systemic therapy such as corticosteroids, propranolol, or interferon alfa-2a or alfa-2b are viable options to inhibit vascular growth and promote involution of the tumor.46–49 Lymphatic Malformations Lymphatic malformations are less common than hemangiomas. They do not undergo spontaneous involution, are usually present at or soon after birth, and grow with the growth of the child.44 They are not true salivary lesions, but they are commonly seen in the submandibular and parotid region in infants and young children.50 Lymphatic malformations are susceptible to infection, with potential for cellulitis, intralesional bleeding, abscess formation, or lymphangiomatous extension to the floor of mouth or trachea with airway compromise. Treatment modalities have been an area of much investigation. Surgical resection must be complete to obviate recurrence. This is often difficult, because of the fragility of the tumor lining, its infiltrative nature, and its proximity to major vessels and branches of the facial nerve.51,52 In an effort to avoid surgical morbidity, success with intralesional sclerotherapy has been demonstrated, resulting in reduction in tumor size and minimal scarring or recurrence.53 Pleomorphic Adenoma Pleomorphic adenomas (benign mixed tumors) are the most common nonvascular benign salivary tumors in children (Fig. 56-6).42,54 They present as firm, rubbery masses, most often in the parotid gland, with an average age at presentation of 9.5 years within the pediatric population.54,55 The tumor
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involving the submandibular or minor salivary glands, concomitant neck dissection and adjuvant radiation therapy is recommended by many institutions.36,64,65 Acinic Cell Carcinoma Acinic cell carcinomas present in a similar fashion as mucoepidermoid carcinomas. They tend to be low grade, and treatment is similar to that of mucoepidermoid carcinoma (Fig. 56-7). Adenoid Cystic Carcinoma Adenoid cystic carcinoma is a rare, high-grade salivary gland tumor. Perineural invasion may result in cranial nerve deficits. There is a high incidence of regional nodal metastases, as well as distant metastases to the lungs, liver, and bone. Treatment includes wide surgical resection, neck dissection, and adjuvant radiation therapy.61 FIGURE 56-6 Pleomorphic adenoma (mixed tumor) of the parotid gland. Epithelial areas are mixed with myxomatoid and chondroid stroma. (Hematoxylin-eosin stain, 50.)
presents as a painless, slowly growing mass and is rarely infiltrative.56 They have variable echogenicity on imaging, with increased heterogenicity seen in larger lesions secondary to necrosis or cystic changes.4 Treatment of superficial lobe tumors includes superficial parotidectomy with facial nerve dissection and preservation. Recurrence rates have been reported to be up to 40%; so, long-term follow-up is recommended.57,58 Simple excisional biopsy should be avoided, because it is associated with a higher recurrence rate. Rarely, recurrent pleomorphic adenomas may undergo malignant degeneration.59
Rhabdomyosarcoma Rhabdomyosarcoma may present as a parotid mass. Histologic variants include undifferentiated and embryonal types (Fig. 56-8). Treatment and outcomes depend on tumor stage and may include wide local surgical resection with radiation and chemotherapy.
Monomorphic Adenomas Monomorphic adenomas are rare in children. Histologically, they may resemble adenoid cystic carcinoma, a highly aggressive malignant salivary tumor.60 Treatment includes complete surgical resection and close long-term follow-up. Papillary Cystadenoma Lymphomatosum (Warthin Tumor) These tumors are most commonly seen in men and are often bilateral parotid lesions. They may rarely present as benign parotid tumors in children.1 Treatment is similar to that for pleomorphic adenomas.
FIGURE 56-7 Acinic cell carcinoma of the parotid gland showing invasive proliferation. (Hematoxylin-eosin stain, 100.)
MALIGNANT NEOPLASMS Malignant salivary neoplasms are rare in children. When present, they are often low-grade lesions, located most commonly in the parotid gland, and have a female preponderance.54 Diagnostic evaluation should include CT or MRI and fineneedle aspiration biopsy. Treatment is surgical, with complete tumor excision with clear margins. Invasive malignancies may require sacrifice of the facial nerve branches. Postoperative radiation therapy is recommended for high-grade lesions.61,62 Mucoepidermoid Carcinoma Mucoepidermoid carcinoma is the most common pediatric salivary malignancy and is most commonly low grade and located in the parotid gland. Surgery is usually curative.39,63 For high-grade mucoepidermoid carcinomas, or those
FIGURE 56-8 Rhabdomyosarcoma of the parotid gland showing spindle cell sarcoma with myogenous differentiation. (Hematoxylin-eosin stain, 100.)
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PART V
HEAD AND NECK
Surgical Considerations ------------------------------------------------------------------------------------------------------------------------------------------------
PAROTID GLAND An S-shaped incision is made, beginning in the preauricular crease and extending in a curvilinear fashion to the postauricular region, followed by an inferior extension to 2 fingerbreadths below the angle of the mandible (Fig. 56-9). Skin
flaps are elevated, and the greater auricular nerve and posterior facial vein will be identified and may need to be sacrificed to expose the posterior border of the parotid gland. Blunt dissection along the tragal pointer and mastoid process, following the posterior belly of the digastric muscle, will allow visualization of the main trunk of the facial nerve as it emerges from the stylomastoid foramen. Meticulous dissection along the facial nerve branches in an anterior direction will elevate
Parotid gland sup. lobe Sup. temporal v. and a.
FACIAL NERVE Mastoid process Gr. auricular ns. Parotid gland deep lobe
Zygoma
Pterygoid fossa Cartilage of external auditory canal
Masseter m. FACIAL NERVE
Mastoid process
FIGURE 56-9 Technique for parotidectomy.
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the superficial lobe of the parotid gland. Careful blunt dissection, with use of the bipolar cautery and facial nerve monitor, will maximize excellent surgical results with minimal morbidity.64,67
SUBMANDIBULAR GLAND For submandibular gland resection, a horizontal skin incision is made in a natural skin crease approximately two fingerbreadths inferior to the body of the mandible. The dissection plane is carried to the investing fascia of the submandibular gland. Exposure should reveal the mylohyoid muscle anteriorly, the sternocleidomastoid muscle posteriorly, and the digastric muscle inferiorly. Identification and division of the anterior facial vein, just deep to this fascia, will facilitate protection of the facial nerve. Anterior retraction of the mylohyoid muscle and downward retraction on the submandibular gland will enable identification of the lingual nerve and Wharton duct. Division of the duct will free the lingual nerve from the gland and allow complete blunt dissection of the gland.66
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Conclusion ------------------------------------------------------------------------------------------------------------------------------------------------
Although salivary gland disorders are rare in childhood, knowledge of the anatomy of the major salivary glands and understanding of both systemic and neoplastic physiology is critical. Neoplasms of the salivary glands are very rare in children and are commonly benign.31,68 Evaluation and management should be tailored to the specific entity. A multitude of diagnostic tools are available and may include radiologic or pathologic studies. Inflammatory and infectious disorders are often treated medically, whereas neoplastic disorders require surgical intervention. Patients and families must be counseled regarding potential short-term and long-term complications of facial nerve injury. Despite the rigorous demands of parotid and submandibular gland surgery, in experienced hands, with adequate monitoring and meticulous dissection and hemostasis, surgical results are excellent.67 The complete reference list is available online at www. expertconsult.com.