CHAPTER 198 Differential Diagnosis of Neck Masses
The presentation of a neck mass in a pediatric patient has many diagnostic possibilities not normally encountered in an adult (Fig. 198-1). Neoplastic disease, especially malignant, is the primary consideration in the evaluation of a neck mass in an adult. In contrast, diagnosis of a pediatric neck mass can be categorized, depending on the location, growth factors, and the child’s age. The possibility of malignancy should always be considered in the differential diagnosis in pediatric patients; however, it is not as overriding a concern as in adults.
The two major categories of pediatric neck masses include congenital and acquired lesions. Congenital masses have a high incidence (>50% in some series),1 which initially differentiates them from acquired masses. The primary type of acquired masses is inflammatory (acute and chronic), which further narrows the differential diagnosis. Benign and malignant lesions are rare in the pediatric patient.
The approach to the child with a neck mass depends on the history and physical examination. Radiographic and laboratory studies may prove helpful, but some masses require surgical biopsy to establish the diagnosis. Thus the pediatric neck mass often poses a challenge to the surgeon.
In the evaluation of a pediatric patient with a neck mass, a detailed history alone can often exclude many lesions in the differential diagnosis. Consideration of temporal relationships can often prove helpful. A history of infection elsewhere in the patient or recent travel or exposure to farm animals may suggest an infectious origin. Preceding trauma may signal a hematoma, whereas an increase in the size of the mass or pain with eating may point to a salivary gland problem. Exposure to drugs such as phenytoin may also be contributory.
The growth characteristics of the neck mass are important. Slow growth suggests a benign process, whereas rapid enlargement occurs with infectious or malignant lesions. Some masses fluctuate in size (e.g., hemangiomas increase in size with straining and crying). Fever, weight loss, night sweats, or fatigue suggest a malignant process.
In the evaluation of a child with a neck mass, comprehensive head and neck examination is essential. Clues to the pathogenesis of the neck mass may be found anywhere in the head. Likewise, a total physical examination should be performed with special attention to other lymph node groups such as the axillae and groin. Palpation for an enlarged spleen should always be attempted.
Infants frequently have small palpable lymph nodes in the posterior cervical region, whereas older children have palpable nodes in the anterior cervical, posterior cervical, and submandibular regions. Any node greater than 2 cm in diameter falls outside the range of these normal hyperplastic nodes and should be evaluated further.
In examination of abnormal lymph nodes or a neck mass, the location is important for determining the site of the precipitating infection or the primary source of a malignant neoplasm. For example, infection in the nasopharynx tends to drain into the posterior cervical region, whereas tonsillitis may cause enlargement in the anterior cervical region. Moussatos2 and Putney3 noted an increased incidence of malignancy in the posterior cervical triangle; in contrast, Torsiglieri and colleagues1 reported an increased incidence in the supraclavicular region.
The consistency of a neck mass is frequently helpful in categorizing the mass. For example, hard masses tend to occur with infection or a malignant process. Fixation of a mass to the skin or deeper structures of the neck suggests a malignancy. A fluctuant mass tends to occur with abscess formation or a cyst.
Depending on the clinical impression of a neck mass from the history and physical examination, selected radiographic studies may help narrow the differential diagnosis. Chest radiography is helpful if a malignancy, sarcoidosis, or pulmonary tuberculosis is suspected. In the evaluation of the nasopharynx, cervical spine, or retropharyngeal region, lateral neck radiography may show an abnormality. Likewise, a sinus series may show evidence of an infection or neoplasm in the paranasal sinuses.
In cases of infection in the neck, computed tomography (CT) with contrast may differentiate cellulitis that may respond solely to antibiotic therapy from an abscess with rim enhancement that may necessitate surgery. CT with contrast also helps identify vascular masses such as hemangiomas. Magnetic resonance imaging (MRI) provides even better detail of soft tissue. When combined with contrast, MRI is also useful in the evaluation of vascular lesions.
Ultrasound of the neck is most helpful in differentiating a cystic structure from a solid mass. It should be included as part of the evaluation of any thyroid mass. Before excision of a thyroglossal duct cyst, ultrasound can confirm the presence of a thyroid gland in its normal position, ruling out the possibility of ectopic thyroid. Use of ultrasound in these cases is easier and more economical. Thyroid scanning remains essential in the evaluation of any thyroid mass.
As with radiography, selected laboratory studies may be useful in the evaluation of the pediatric neck mass. A complete blood count with differential is indicated if a malignancy or systemic infection is suspected. Serologic testing for Epstein-Barr virus (EBV), cytomegalovirus, toxoplasmosis, syphilis, or cat-scratch disease may be diagnostic. An elevated serum calcium level is highly suggestive of sarcoidosis, whereas thyroid function studies are necessary in the evaluation of most thyroid masses. Urinary collection for vanillylmandelic acid (VMA) is helpful when neuroblastoma is suspected. Although not as accurate as a culture of infected tissue, skin tests, if available, remain a reliable indicator of mycobacterial disease.
Although fine-needle aspiration of a suspected malignancy is not as reliable in children as in adults, fine-needle aspiration of a neck infection decompresses the mass and provides material for culture. In some cases, especially when the diagnosis of malignancy is considered, an incisional or excisional biopsy is indicated. Advantages of a biopsy include inspection of the lesion, providing a cuff of healthy surrounding tissue and tissue for frozen and permanent section, electron microscopy, and tumor markers.
Although the definitive mechanism for the development of branchial cleft cysts is unclear, it is suspected that these congenital masses result from the cervical sinus of His becoming entrapped without an external or internal opening. An epithelium-lined cyst results. Others suggest that these cysts develop from epithelial rests of tissue from Waldeyer’s ring.4 Branchial cleft cysts are relatively common; in one series, they comprise one third of congenital neck masses.1
Branchial cleft cysts typically are seen as nontender, fluctuant masses that may become inflamed and abscess during an upper respiratory infection (Fig. 198-2). First branchial cleft cysts, although rare, typically present near the angle of the mandible (Fig. 198-3). Second branchial cysts are found high in the neck and deep to the anterior border of the sternocleidomastoid muscle. Third branchial cleft cysts, also rare, are seen near the upper pole of the thyroid gland. Other symptoms, depending on the size of the cyst, include dysphagia, dyspnea, and stridor.
Figure 198-3. First branchial derivatives present as a pit or a mass near the angle of the mandible (arrow). They frequently originate in or near the external canal and, during their course, involve the facial nerve.
Radiologic evaluation of a branchial cleft cyst may include ultrasound, CT, and MRI. Ultrasound shows a fluid-filled cyst and can differentiate cystic lesions from solid masses. CT and MRI also confirm the cystic characteristics of the mass and, more importantly, delineate the relationship of the cyst to surrounding structures (Fig. 198-4).
Thyroglossal duct cysts form in a persistent thyroid descent tract that begins as an elongation of the thyroid diverticulum. Beginning at the foramen caecum of the tongue, this tract may extend to the thyroid gland itself, where some tissue may persist in the region of a pyramidal lobe. These remnants are cysts and are not associated with a cutaneous sinus or fistula tract unless surgically drained and inadequately excised. They comprise approximately one third of congenital neck masses in children.1
Most thyroglossal duct cysts are seen in the midline near the level of the hyoid bone because the tract passes just anterior to the hyoid bone (Fig. 198-5). Some cysts may present laterally and are not infrequently found superior to the hyoid or as low as the level of the thyroid gland. Thyroglossal duct cysts that occur off the midline may be difficult to differentiate from branchial cleft cysts, an important factor in their surgical excision. Other unusual presentations of thyroglossal duct cysts include formation on either side of the hyoid bone as dumbbell-shaped lesions and, rarely, as cystic lesions in the larynx. Thyroid tissue is found in surgical specimens in up to 45% of cases.5
A thyroglossal duct cyst usually presents as an asymptomatic mass but may be associated with mild dysphagia. Not infrequently, presentation of these cysts may be accompanied by infection, causing rapid enlargement that may produce significant dysphagia and choking.
In cases in which a thyroglossal duct cyst is suspected, it is important to differentiate ectopic thyroid from a cyst. Although only 10% of ectopic thyroid is found in the neck, it may represent the only thyroid tissue in 75% of patients.6 Children with ectopic thyroid may be mildly hypothyroid; however, excision of this tissue necessitates hormone replacement for the remainder of the patient’s life. Thyroid ultrasound and radionucleotide scanning can differentiate ectopic thyroid from a thyroglossal duct cyst; ultrasound is easier to perform, less expensive, and does not use radioisotopes.
The Sistrunk operation is the standard method of thyroglossal duct cyst excision. The cyst is excised along with a cuff of tissue including the center portion of the hyoid bone. Incision and drainage of an infected cyst should be avoided because violation of the cyst capsule may invite recurrence. Recurrence rates of nearly 10% have been reported in children who have undergone uncomplicated Sistrunk operations.1
The term lymphatic malformation is a better definition of the lesion that was previously termed lymphangioma. Lymphatic malformations are congenital malformations of lymph tissue that result from the failure of lymph spaces to connect to the rest of the lymphatic system. Lesions containing both lymphatic and venous components may be labeled combined venolymphatic malformations. Macrocystic lymphatic malformations (previously termed cystic hygroma) contain large thick-walled cysts that have less infiltration of surrounding tissue. Microcystic lymphatic malformations have more extensive infiltration of the soft tissue structures of the head and neck, especially in the tongue and floor of mouth, making their excision difficult.
A lymphatic malformation presents as a soft, smooth, nontender mass that is compressible and can be transilluminated (Fig. 198-6). Typically, lymphatic malformations fluctuate in size as a result of infection or hemorrhage. They mostly impact the cosmetic appearance of the child. Depending on the size and location of the mass, there may be respiratory compromise and difficulty in feeding.
Radiographic evaluation with MRI or CT is invaluable for diagnosis and determination of the extent of the lesion. Radiography shows fluid-filled spaces with surrounding connective tissue. Because these malformations lack a capsule and extend along the lymphatic channels, MRI or CT is essential in defining normal anatomic structures that should be preserved when surgical excision is performed.
The goals of surgery are to improve cosmetic appearance and to counter impaired breathing or eating. Because of the infiltrative nature of these malformations, complete surgical excision is often difficult; debulking of the mass often accomplishes these goals.
Some experts recommend staging of surgical excision in extensive cases.7 Management with radiotherapy has not been effective.8 Macrocystic lesions can be treated with sclerotherapy using alcohol. An experimental lyophilized streptococcal compound, OK-432, has been used successfully to sclerose macrocystic lesions.9
Hemangiomas are proliferative endothelial lesions rather than true neoplasms. Hemangiomas present at birth, grow rapidly during the first year of life, and begin to slowly involute at 18 to 24 months of age. Hemangiomas occur in up to 10% of children with a female-to-male ratio of 2 : 1.10
Hemangiomas are seen as red or bluish soft masses that frequently have a skin component. Typically, these masses are compressible and increase with straining or crying. With large hemangiomas, a bruit may be heard over the lesion. CT or MRI with contrast often confirms the diagnosis of a vascular lesion (Fig. 198-7).
Because hemangiomas typically involute after several years, the usual management is observation, unless there is functional impairment, bleeding, skin necrosis, or a coagulopathy caused by thrombocytopenia. Use of systemic corticosteroids may be helpful in the management of complications such as skin ulceration, dysphagia, dyspnea, thrombocytopenia, or cardiac failure.11–14 Surgical excision or laser therapy may be helpful in cases of incomplete involution or when mild functional or cosmetic abnormalities remain. Management with radiotherapy may lead to malignant transformation, and the use of sclerosing agents and cryotherapy has produced poor results.8,15
Teratomas in the head and neck are rare, comprising only 3.5% of all teratomas in one series.16 Although there is a female-to-male preponderance of 6 : 1 in other body regions, the female-to-male ratio is equal in the head and neck.17 Teratomas arise from pluripotential cells and consist of tissues foreign to the site from which they arise. A history of maternal polyhydramnios has been noted in up to 18% of neonates who have a cervical teratoma (Fig. 198-8).