American Journal of Neuroradiology 26:1575-1579, June-July 2005
© 2005 American Society of Neuroradiology
PEDIATRICS
Nasopharyngeal Carcinoma: Recognizing the Radiographic Features in Children
Hilda E. Stambuka,
Snehal G. Patelb,
Kristine M. Mosiera,
Suzanne L. Woldenc and
Andrei I. Holodnya
a Department of Radiology, Division of Neuroradiology, Memorial Sloan-Kettering Cancer Center, New York, NY
b Department of Surgery, Head and Neck Service, Memorial Sloan-Kettering Cancer Center, New York, NY
c Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, NY
Address reprint requests to Hilda E. Stambuk, MD, Division of Neuroradiology, Memorial Sloan Kettering Cancer Center, 1275 York Avenue C-128, New York, NY 10021
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Abstract
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BACKGROUND AND PURPOSE: Children often present with enlargement
of the nasopharyngeal soft tissues, which is usually due to
benign hypertrophy of adenoids. The objective of this report
is to emphasize that, although rare, nasopharyngeal carcinoma
(NPC) does occur in children and can be diagnosed reliably when
certain key radiographic features are recognized.
METHODS: The presenting scans of 11 patients with biopsy proven NPC were reviewed retrospectively by a CAQ-certified neuroradiologist. The age range was 12–17 years (median 15 years). Fifteen scans were reviewed, including 8 CT scans of the neck with intravenous contrast and 7 MR scans of the nasopharynx without and with gadolinium.
RESULTS: All 11 patients had a nasopharyngeal mass. The nasopharyngeal mass had invaded the central skull base in 10 patients (91%). Widening of the petroclival fissure was present in 8 (73%) patients; all except one patient had accompanying skull base invasion. The tumor had extended into the adjacent parapharyngeal space in 6 (55%), the pterygopalatine fossa in 2 (18%), and the masticator space in 2 (18%). Unilateral cervical lymphadenopathy was present in 4 (36%) and bilateral in 7 (64%). Lateral retropharyngeal lymphadenopathy that measured greater than 1 cm in maximal transverse dimension was present in 10 (91%).
CONCLUSION: Pediatric NPC is generally not suspected clinically until late into the disease process. Awareness that NPC can occur in children should prompt careful evaluation for distinctive radiographic features. Earlier diagnosis may then direct the patient to timely appropriate therapy when these key radiographic features are present and recognized.
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Introduction
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Benign adenoidal hypertrophy (BAH) is far and above the most
common cause of a mass in the posterior nasopharynx in children.
Malignant tumors of the nasopharynx are rare in this age group
and the histology generally varies with the age of the patient
at presentation. Sarcomas and lymphomas are more common in younger
children, whereas carcinoma of the nasopharynx (NPC) has a predilection
for adolescents and teenagers (
1). Unfortunately, these tumors
tend to be locally advanced by the time they are diagnosed mainly
because the clinical presentation is non-specific (
2). Additionally,
because they are rare, they may not be high on the list of differential
diagnoses in children who present with a nasopharyngeal mass.
The therapeutic implications of a delayed diagnosis of nasopharyngeal
carcinoma (NPC) can be significant (
3). The objective of this
report is to emphasize that, although rare, nasopharyngeal carcinoma
does occur in children and can be diagnosed reliably when certain
key radiographic features are recognized.
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Methods
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The study population included 11 patients under the age of 18
years with previously untreated NPC diagnosed at our institution
from March 1995 to July 2004. Retrospective chart review was
carried out to collect pertinent clinical and pathologic data
after obtaining institutional review board approval. All patients
had histopathologically documented undifferentiated carcinoma
of the nasopharynx.
Table 1 is a summary of the patients’
demographics and clinical characteristics. The age range was
12–17 years with a median age of 15 years. There were
4 female and 7 male patients. All patients had locally advanced
disease and were staged using AJCC staging system (
4). All CT
scans were performed with intravenous contrast employing contiguous
5-mm slice thickness, average field of view of 22 cm, and a
512
x 512 matrix. MRI scans were performed with a slice thickness
of 5 mm (skip 1 mm) or 4 mm (skip 1 mm), most commonly with
an 18 cm field of view and a 256
x 224 matrix. All MRI scans
were performed without and with intravenous contrast. There
were a total of 8 CT scans and 7 MRI scans; 4 patients had both
CT and MRI scans. These pre-treatment films were retrieved and
reviewed for key radiographic features
(Table 2) by a CAQ-certified
neuroradiologist (H.E.S.) who was not blinded to the purpose
of the review.
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Results
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Table 2 is a summary of the radiographic findings at diagnosis.
All patients had an asymmetric mass in the posterior nasopharynx.
The mass extended anteriorly to the posterior choana in 7 patients
(64%) and into the nasal cavity in an additional two patients
(18%). The nasopharyngeal mass had invaded the central skull
base in 10 patients (91%). Widening of the petroclival fissure
was present in 8 (73%) patients; all except one patient had
accompanying skull base invasion. Ten (91%) patients had unilateral
postobstructive mastoid opacification and 1 (9%) had bilateral
partial opacification. The tumor had extended into the adjacent
parapharyngeal space in 6 (55%), into the pterygopalatine fossa
in 2 (18%) and the masticator space in 2 (18%). Unilateral cervical
lymphadenopathy was present in 4 (36%) and bilateral in 7 (64%).
Lateral retropharyngeal lymphadenopathy that measured greater
than 1cm in maximal transverse dimension was present in 10 (91%).
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Discussion
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The National Cancer Institute estimates that approximately 12,400
children and adolescents younger than 20 years of age are diagnosed
with cancer in the United States each year. Sarcomas of the
soft tissue and bone occur more commonly than malignant epithelial
tumors within the head and neck region in children. Carcinoma
of the nasopharynx accounts for less than 1% of all childhood
cancers (
1) and children aged between 10 and 19 years are the
most common age-group affected. The clinical experience in diagnosis
and treatment of this condition is therefore limited. Benign
adenoidal hypertrophy, on the other hand is by far the most
common cause of a mass of the posterior nasopharynx in children.
In light of this fact, NPC is unlikely to be considered in the
differential diagnosis unless the radiologist is aware that
NPC can occur in children and therefore deliberately looks for
associated secondary diagnostic signs. The objective of this
study was to describe salient radiologic features that might
help diagnose the condition.
When evaluating significant masses in the posterior nasopharynx, the age of the pediatric patient is an important consideration in narrowing the differential diagnosis. For example, rhabdomyosarcoma or lymphoma is the more likely diagnosis in younger children where as NPC or lymphoma is more common in adolescents (1). The association of non-keratinizing NPC to Epstein-Barr virus (EBV) is well known, and the virus has been associated with NPC in children as well (5). EBV blood titers, however, are of little supplemental value to the imaging findings because of the widespread prevalence of elevated titers in the general population. Children with NPC generally present with neck mass and/or nasal symptoms such as obstruction, bleeding and discharge or fever of unknown origin (2). These patients are generally treated with several courses of antibiotics without response, and ultimately require a biopsy to exclude other pathology such as NPC or lymphoma. However, there are no specific symptoms that point to the diagnosis of NPC. NPC is primarily a disease of adults and its incidence in children varies with geographic location. In China, where there is a high frequency of this tumor, less than 1% of NPC occurs in children under 14 years of age. By comparison, 10–20% of NPC in Tunisia, Uganda, Kenya, Nigeria, and Sudan occur in children (6). In the United States there are reports of higher prevalence of NPC in African Americans, but the relationship of ethnicity to NPC in children is unclear (7).
The primary echelons of lymphatic drainage from the nasopharynx include the lateral retropharyngeal, high level II and high level V lymph nodes (8). The lateral retropharyngeal lymph nodes are therefore commonly involved in NPC as seen in the majority of our patients. In addition, all of our patients also had cervical lymphadenopathy. Adenoidal hypertrophy is also frequently associated with cervical and to a lesser degree retropharyngeal lymphadenopathy in the normal pediatric population making the diagnosis of NPC difficult. Therefore, presence or morphology of enlarged lymph nodes is not diagnostic in isolation. In addition, the morphologic appearance of reactive lateral retropharyngeal lymph nodes can be difficult to distinguish from metastatic lymphadenopathy (9).
Certain radiographic features of the primary tumor can however be very useful in differentiating NPC from benign adenoidal tissue (10, 11). In contrast to benign masses, the configuration of NPC is almost always asymmetric (Fig 1). Local spread of the tumor outside the confines of the nasopharynx is dictated in large measure by the local anatomy. The pharyngobasilar fascia acts as a barrier to local spread of the tumor and tends to direct the advancing tumor towards the central skull base (clivus). Skull base invasion is therefore frequently seen with locally advanced tumors and occurred in the majority of our patients. Invasion of the skull base is more easily recognized on MRI imaging than CT by changes in the marrow signal of the clivus. As demonstrated in Figure 2, patients with involvement of the marrow have decreased signal on T1-weighted images, enhancement post contrast administration and generally increased signal on T2-weighted images. Widening of the petroclival fissure due to infiltration by tumor is best appreciated on CT bone windows and was present in 73% of our patients (Fig 3). Later in the course of the disease, the tumor breaches the pharyngobasilar fascia and gains access to the parapharyngeal space.
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FIG 1. The configuration of NPC is almost always asymmetric as seen in this contrast enhanced, axial T1 weighted fat saturation MRI image (TR = 400, TE = 10.3).
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FIG 2. Central skull base invasion. Note high signal in the left aspect of the clivus on this axial, T2 weighted fat saturation MRI image. (TR = 2000, TE = 105).
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FIG 3. Tumor extending into and widening the right petroclival fissure (arrows). Soft tissue (A) and (B) bone windows CT neck with contrast.
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Gross parapharyngeal space invasion was present in just over one half of our patients (Fig 4). More subtle involvement of the parapharyngeal space may be difficult to appreciate, especially if the radiologist does not have NPC on the list of differential diagnoses. Norton et al (12) have suggested that violation of the nasopharyngeal plexus that appears as an enhancing line around the pharyngobasilar fascia may be indicative of an infiltrative tumor. Tumor can also extend to the pterygopalatine fossa causing widening that is easy to detect on CT (Fig 5) and MRI. This finding is however, not common and occurred in less than 20% of our patients. Finally, on rare occasions the tumor can spread into the masticator space to involve the muscles of mastication (Fig 6).
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FIG 5. Tumor extension into and widening of the right pterygopalatine fossa (arrow) seen on soft tissue window image (A) and three consecutive bone window images (B-D) CT neck with contrast.
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FIG 6. Tumor invading the left masticator space. Axial T2 weighted fat saturation MRI image. (TR = 2000, TE = 105).
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The presence of an asymmetric nasopharyngeal mass in itself may not necessarily arouse the suspicion of NPC in children. However, as we have pointed out, the index of suspicion for NPC should be higher if any of the associated radiographic features can be demonstrated.
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Conclusion
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Pediatric NPC is generally not suspected clinically until late
into the disease process. Awareness that NPC can occur in children
should prompt careful evaluation for distinctive radiographic
features. Earlier diagnosis may then direct the patient to timely
appropriate therapy when these key radiographic features are
present and recognized.
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Footnotes
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Presented in part at the 40th Annual Meeting of The American
Society of Neuroradiology, Vancouver, BC, May 2002.
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References
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- Barnes L, Brandwein M, Som PM. Diseases of the nasal cavity, paranasal sinuses, and nasopharynx. In: Barnes L, ed. Barnes Surgical Pathology of the Head and Neck. 2nd ed. New York: Marcel Dekker, Inc; 2000
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- Ichimura K. Can Rouviere’s lymph nodes in non-malignant subjects be identified with MRI? Auris Nasus Larynx 1993;20:117–123[Medline]
- Chin SC, Fatterpekar G, Chen CY, Som PM. MR imaging of diverse manifestations of nasopharyngeal carcinomas. AJR Am J Roentgenol 2003;180:1715–1722[Free Full Text]
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Received August 12, 2004;
accepted after revision November 11, 2004.
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Abstract
Introduction