Arjun Sahgal2, Girish Fatterpekar3, Eugene Yu4
1Radiology Resident, University of
Toronto, 263 McCaul Street, 4th Floor, Toronto, Ontario, Canada
2Associate Professor of Radiation Oncology and Surgery,
University of Toronto Deputy Chief of Radiation Oncology, Sunnybrook Odette
Cancer Centre 2075 Bayview Avenue Toronto, Ontario, Canada M4N 3M5
3Associate Professor of Radiology, New York University Langone
Medical Center 660 First Avenue Floor 2 Room 224 New York, New York 10016
4Associate Professor of Medical Imaging and
Otolaryngology, Head and Neck Surgery, University of Toronto Princess Margaret
Cancer Centre 610 University Avenue Room 3-959 Toronto, Ontario, Canada M5G 2M9
author: Eugene Yu; Email:
Citation: Chan M, Sahgal A, Fatterpekar G, Yu E. Imaging of Nasopharyngeal Carcinoma. J Nasopharyng Carcinoma, 2014, 1(11): e11. doi:10.15383/jnpc.11.
Competing interests: The authors have declared that no competing interests exist.
Conflict of interest: None.
Copyright: 2014 By the Editorial Department of Journal of Nasopharyngeal Carcinoma.
This is an open-access article distributed under the terms of the Creative
Commons Attribution License, which permits unrestricted use, distribution, and
reproduction in any medium, provided the original author and source are
Abstract: Nasopharyngeal carcinoma (NPC) is the most common primary neoplasm to
arise in the nasopharynx. It is an aggressive tumor with a propensity for local
tumour invasion and a high incidence of metastases to cervical lymph nodes. Due
to its central location in the nasopharynx, primary tumours have many potential
routes of local spread, including into important spaces such as the orbital and
intracranial spread. This article discusses the current imaging
techniques used in the diagnosis and staging of nasopharyngeal carcinoma, and
reviews the 7th edition of the
International Union Against Cancer (UICC) and American Joint Committee on
Cancer (AJCC) TMN staging system for nasopharyngeal carcinoma.
Nasopharyngeal carcinoma (NPC), the most common neoplasm to arise in the
nasopharynx, is a locally aggressive tumor with a high incidence of cervical
nodal metastases. It typically arises from the epithelial lining of the lateral
nasopharyngeal wall, particularly inthe lateral pharyngeal recesses.
Histologically, the World Health Organization classifies NPC into
threesubtypes: keratinizing squamous cell carcinoma (type 1), non-keratinized
carcinoma (type 2), and undifferentiated carcinoma (type 3). The tumor has a
propensity towards extensive invasion into adjacent tissues, particularly
laterally into the parapharyngeal space and superiorly into the skull base.
However spread to the palate, nasal cavity, and oropharynx have also commonly
reported. Distant metastases can arise within bone, lung, the mediastinum and,
more rarely, the liver . Although NPC is rare in North America and Europe
with an incidence of 0.5-2 per 100,000, intermediate incidence rates are seen
in Southeast Asia, the Mediterranean Basin, and the Arctic ranging from 0.5 to
31.5 per 100,000 person-years in males and 0.1 to 11.8 person-years in females
[2, 3]. In southern China, NPC is endemic with overall NPC incidence rates
reaching 20-30 per 100,000 person-years and 15-20 per 100,000 person-years
amongst males and females, respectively, in the province of Guangdong [4, 5]. NPC has a
male to-female ratio of2-3:1 , and is
most common among patients 40–60 years old with bimodal age peaks in the
second and sixth decades of life .
The etiology of NPC is multifactorial, involving both environmental and
genetic risk factors. Diets high in salt-preserved foods – such as the
salted fish, meat, eggs, fruits, and vegetables in a Southern Asian diet
– have been identified as possible causative agents acting through the
carcinogen, N-nitrosodimethylamine . Studies have also indicated a
causal role for the Epstein-Barr virus (EBV) with EBV DNA, RNA, and gene
products detected in tumor cells .
Role of Imaging
Imaging plays an important role in all stages of NPC management, from
diagnosis and staging to treatment and follow-up. Since up to 10% of primary
NPC tumors are missed on endoscopy [8, 9], cross-sectional imaging studies,
such as magnetic resonance imaging (MRI) or computed tomography (CT), are
required for diagnosis. Imaging also allows forassessment of the exact
boundaries of pharyngeal wall involvement and tumor invasion into surrounding
structures. One study demonstrated diagnostic sensitivity and specificity of
100% and 93% for MR imaging, 90% and 93% for endoscopy, and 95% and 100% for
endoscopic biopsy, respectively . Currently, MRI and CT are not routinely
used for screening purposes; however, the radiologist should consider NPC in
high-risk patients, such as those of Asian descent being evaluated for otitis
media or with incidental findings of middle ear opacification.
Cross sectional imaging contributes to both prognosis and treatment
planning [10, 11].MRI is currently the imaging modality of choice for tumor
staging and nodal assessment due to its superior soft tissue resolution and
excellent ability to assess primary tumor invasion into surrounding soft tissue
and bony structures, such as the pharyngobasilar fascia, sinus of Morgagni,
skull base, cavernous sinus, and nerves [11-13]. MRI is also more reliable for
differentiating between the primary tumor and retropharyngeal adenopathy
The staging MRI protocol for NPC will vary from center to center. In
general, the images should cover the area from above the frontal sinuses to the
thoracic inlet on axial studies, and from the tip of the nose to the fourth
ventricle on coronal sequences. At our institution, axial and coronal T1- and
T2-weighted images, as well as a sagittal T1 or T2 fat saturation series
covering these regions are obtained. A head and neck imaging coil is routinely
used for both the 1.5T and 3.0T MRI scanners. The axial, coronal and sagittal
T1 series are performed using a T1-FLAIR technique. Post gadolinium-enhanced
axial images with fat saturation and coronal images without fat saturation are
also acquired using a conventional spin echo T1 technique. A study by Lau et
al. found that the axial pre-contrast and post-contrast series were the
most informative MRI sequences for evaluating primary tumor extension and
achieved approximately 100% diagnostic accuracy in T-staging of NPC . We
find that a combination of axial and coronal T2 and non-contrast T1-weighted
images are the best for providing detailed views of the local NP anatomy and
surrounding structures.Post-contrast images also allow for accurate assessment
of perineural disease along major nerves, as well as the cavernous sinus .
Early findings of NPC on imaging include asymmetry of the nasopharynx
and an obstructed Eustachian tube (ET) . Most NPC masses originate in
the fossa of Rosenmüller, otherwise known as the lateral pharyngeal
recess. NPC has been shown to spread in a step-wise pattern via
paths of least resistance, such as via the neuroforamina . Critical structures located near the nasopharynx including the cavernous sinus, pituitary
gland, orbit, and brainstem must be accurately evaluated for disease
involvement so that they can be appropriately treated, or more importantly,
spared from unnecessary radiation dose if they are deemed to be clear of
disease. On T2-weighted images, NPC
usually exhibits an intermediate signal that is mildly hyperintense to muscle,
while on T1-weighted images, NPC has a signal intensity that is hypo- to
isointense to muscle. With contrast administration, the tumor tends to enhance
less than normal mucosa, but more than muscle.
CT has a role in the assessment of bony skull base involvement .
However, CT is inferior to MRI for delineating soft tissue involvement, and it
is often difficult to differentiate NPC from hypertrophied lymphoid tissue. For
patients with advanced N3 nodal stage and/or clinical evidence of distant
metastases, positron emission tomography–computed tomography (PET-CT) may
be performed [7, 22].PET has been shown to be superior to CT and MRI for the detection of
nodal disease, as well as for the diagnosis of local residual or recurrent NPC
[23, 24]. A study by Comoretto et al. demonstrated that the combined use
of MRI and FDG PET-CT had a greater diagnostic accuracy for detecting residual
or recurrent disease compared to either modality individually . In
addition, PET is reportedly useful for differentiating recurrent NPC tumors
from post-radiation changes, such as tissue necrosis, fibrosis and edema [23,
26-29]. However, in the early post-radiation period, FDG uptake can be elevated
secondary to inflammation following radiotherapy. Higher sensitivity and
specificity is achieved when PETimaging is performed at least 3 to 4 months
Follow-up evaluation involves a baseline imaging study that is typically
performed 2 to 3 months after completion of radiation treatment, followed by
imaging every 3 to 6 months for the first 2 post treatment years .Any soft
tissue signal abnormalities on MRI in the nasopharynx, deep face or skull base,
should remain stable over this period or show further reduction in
volume.Recurrent disease is seen as any increase in the volume of abnormal
signal from baseline imaging.Most recurrences, localor systemic, occur within
the first 2 years after treatment . Of the patients with recurrence, 10% to
20% may be curable with additional treatment . After 2 years without
evidence of recurrence, the imaging interval is typically extended to every 6
to 12 months.Although not yet the mainstay of patient follow up, one
meta-analysis demonstrated that FDG-PET/CT is more sensitive and specific than
CT and MRI for the diagnosis of local residual
or recurrent NPC .
Anatomy of the Nasopharynx
The nasopharynx is the superior-most aspect of the aerodigestive tract.
The space opens anteriorly to the nasal cavity through the nasal choanae and
inferiorly to the oropharynx at the level of the hard palate or the C1/2
junction. The roof of the nasopharynx abuts the sphenoid sinus floor, and
slopes posteroinferiorly along the clivus to the upper cervical vertebrae.
Laterally, it is limited by the margins of the superior constrictor muscle, the
pharyngobasilar fascia (PBF), and the parapharyngeal space (PPS). Involvement
of the PPS, a fibrofatty space separating the nasopharynx from the masticator
space, serves as an important marker for tumor staging. The posterolateral
limits of the nasopharynx consist of the carotid space, which is essentially
synonymous with the post-styloid parapharyngeal space. The walls of the
nasopharynx are lined with mucosa comprised of squamous epithelium, a muscular
layer, and a fibrous layer consisting predominantly of the PBF. Remains of
adenoid tissue may persist into adulthood and exist as tags in the roof of the
nasopharynx. The buccopharyngeal fascia, which is derived from the middle layer
of the deep cervical fascia, forms a fascial sling around the lateral and
posterior portions of the nasopharynx and provides a fascial limit to
The pharyngobasilar fascia is a tough aponeurosis connecting the
superior constrictor muscles to the skull base. This important structure
extends from the posterior margin of the medial pterygoid plate anteriorly and
the occipital pharyngeal tuber and prevertebral muscles posteriorly to the
superior pharyngeal constrictor inferiorly. The PBF is continuous with the
foramen lacerum, which is a fibrocartilaginous structure that forms part of the
floor of the horizontal carotid canal and roof of the nasopharynx. It is a
route for the extension of naspharyngeal tumors into the cavernous sinus and
The torus tubarius is a prominent anatomical landmark corresponding to
the mucosal-lined projection of the distal cartilaginous ends of the paired
Eustachian tubes into the lumen of the nasopharynx. It can be visualized at the
superior aspect of the posterolateral walls. The ostia of the Eustachian tubes
are located anterior and inferior to the torus tubarius(Figure 1). The
Eustachian tubes and the medial fibers of the levator veli palatine muscle
penetrate into the nasopharynx through the sinus of Morgagni, which is a
posterolateral defect in the pharyngobasilar fascia where muscular fibers are
absent. Given this anatomical characteristic, the sinus of Morgagni is an
important route for malignant dissemination into adjacent spaces, including the
parapharyngeal space. Located posterior and superior to the torus tubarius, the
lateral pharyngeal recess originates in a mucosal herniation through the sinus
of Morgagni. It is the most common site of origin of NPC. The
salpingopharyngeal fold, which forms the anterior limit of the lateral
pharyngeal recess, is a mucosal protrusion overlying the salpingopharyngeus
of these mucosal landmarks is a common incidental finding, especially
the lateral pharyngeal recesses, and should not be mistaken for tumors.
The retropharyngeal space, a potential space containing the medial and
lateral retropharyngeal lymph nodes (RPN), is located posterior to the
nasopharynx. The lateral retropharyngeal lymph nodes, also known as the nodes
of Röuviere, are the first nodes of lymphatic drainage along with Level II
cervical nodes, and thus, are reported to be the most common site of nodal
metastases . These nodes can be visualized on MRI from the skull base to
the level of C3. The medial retropharyngeal nodes do not form a discrete chain
and are not visible on imaging.
Other important structures include the foramen rotundum and pterygoid
(or Vidian) canal, which communicate with the pterygopalatine fossa and are
thus potential routes of perineural tumor spread.
Figure 1. Axial T2 weighted image showing the anatomic features of the
nasopharynx. Torus tubarius TT, Eustachian tube opening (*), tensor veli
palatini (short arrow), levator veli palatini (long arrow), longus musculature
Staging of NPC
Currently, the 7th edition of the International Union Against
Cancer (UICC) and American Joint Committee on Cancer (AJCC) TMN staging system
is used, which was revised and released in January 2010.
As previously described, most cases of NPC originate in the lateral pharyngeal
recess and spread submucosally
with early infiltration into deeper neck spaces. NPC tends to have
well-defined patterns of spread.
Primary Tumor (T) Stage T1
Stage T1 refers to disease that is confined to the nasopharynx (Figure
2), as well as disease with extension inferiorly to involve the oropharynx or
anteriorly to involve the nasal cavity. This stage includes all tumors
that are superficial to the pharyngobasilar fascia, with no evidence of PBF
The nasal cavity is commonly involved in NPC. Stage T1 disease also
includes tumors with anterior extension beyond the plane of the posterior
choanae into the nasal cavity (Figure 3). The nasal cavity represents the most
common route for direct tumor invasion into the pterygopalatine fossa via the
sphenopalatine foramen. Oropharyngeal extension is readily noted on coronal or
sagittal MR imaging as tumor that has extended inferiorly past the plane of
palate.On axial sections, the oropharynx is considered involved when tumor is
seen inferior to the C1/C2 junction.
Figure 2. Axial T1
weighted image shows a left sided tumor mass (*) localized to the nasopharynx
Figure 3. Axial T2 weighted image shows anterior extension of a nasopharyngeal
carcinoma into the right posterior nasal cavity (arrow). This is still T1
Stage T2 refers to disease that has invaded beyond the PBF and
infiltrated posterolaterally into the parapharyngeal space. This stage is
associated with an increased risk of tumor recurrence and distant metastases
[31-34]. It is recognized on imaging as a breach of tumor beyond the
intrapharyngeal portion of the levator veli palatini muscle, or infiltration of
the tensor veli palatini (which is a thin strip of muscle located lateral to
the levator veli palatini).Advanced PPS disease is demonstrated on imaging as
the presence of tumor mass invading into the hyperintense fat of the PPS
(Figure 4). From here, further progression can see involvement of the
poststyloid PPS structures, such as the carotid sheath.
Posterior or retropharyngeal tumorspread is common in NPC. This refers
to disease that has invaded posteriorly to involve the longus musculature and
prevertebral space. This region contains lymphatics and a venous plexus, which
increases the risk of distant metastases. At present, the current UICC/AJCC
system does not specifically make note of the presence of prevertebral disease
extension in the staging scheme.
Figure 4. Parapharyngeal tumor extension (T2). Note that the left sided
mass has extended laterally to infiltrate across the levator and tensor veli
palatini musculature. Tumor is also present within the prestyloid
parapharyngeal fat (short arrow) ad has extended to become intimate with the
left internal carotid artery (long arrow).
Stage T3 refers to disease that is characterized by involvement of the
bony structures of the skull base and/or the paranasal sinuses. Superior extension
of NPC is the most frequent route of direct extension, with the most common
sites of involvement being the clivus, pterygoid bones, body of the sphenoid
bone, and apices of the petrous temporal bones . Skull base invasion is
seen in up to 60% of NPC patients at diagnosis [36, 37]. Assessment for skull
base involvement can be achieved with T1-weighted MRI sequences or CT, and
should focus on five key regions: clivus, right pterygoid base, left pterygoid
base, right petrous apex, and left petrous apex . On T1-weighted images,
bony involvement is demonstrated as replacement of the normal hyperintense MR
signal of fatty yellow bone marrow with an intermediate or low signal, which
can is indicative of reactive change and/or actualtumorinvasion (Figure 5). CT
will show the presence of bony cortical loss and medullary soft tissue lytic
Involvement of the paranasal sinuses can result from direct tumor
extension. Maxillary sinus involvement is rare and is usually a late finding
occurring after nasal or infratemporal maxillary wall erosion in the setting of
extensive disease. Involvement of the ethmoid sinus usually occurs via direct
spread from the sphenoid sinus or nasal cavity. With ethmoid sinus involvement,
the optic nerves become more vulnerable to the radiation dose during radiation
therapy. Sphenoid sinus involvement is common in NPC as tumor will extend
superiorly through the sphenoid sinus floor (Figure 6). Infiltration of a sinus
can be visualized as opacification with fluid or tumor, and loss of contiguity
of the sinus walls.
A B C
Figure 5A, B, C: 5A is a sagittal T1 weighted image showing a lobulated
NPC (*). Note the replacement of the normal hyperintense fatty marrow signal within
the adjacent overlying clivus (arrow). 5B and 5C are coronal T1 images from
another patient showing the presence of abnormal intermediate T1 signal within
the right body of the sphenoid (arrow in 5B) and the right petrous temporal
bone apex (PA) and clivus (arrow in 5C).
Figure 6. Coronal T1 image following gadolinium contrast administration
shows superior extension of a large NPC (*) into the right sphenoid sinus
refers to instances with intracranial extension and/or involvement of
the cranial nerves, hypopharynx, orbit, or masticator space. NPC has a
propensity for invasion of the skull base foramina and their corresponding
nerves or vessels – such as the foramen rotundum (containing the
maxillary nerve), foramen ovale (containing the mandibular nerve), foramen
lacerum (containing the internal carotid artery), and the vidian canal
(containing the vidian artery and nerve). The foramen ovale and lacerum are the
most common routes for tumor extension into the intracranial cavity (Figure 7).
Such nerve involvement will signify stage T4 disease. Assessment of the skull
base foramina is best achieved on coronal imaging. Less common findings include
invasion of the hypoglossal nerve canal (containing the hypoglossal nerve) and
jugular foramen (containing cranial nerves IX-XI). Disease involving the
pterygopalatine fossa is important as it is an important crossroads that
connects with a number of other anatomic regions. Disease reaching the pterygopalatine
fossa can spread: (1) in a perineural fashion along the maxillary nerve through
the foramen rotundum into the middle cranial fossa, (2) posteriorly through the
vidian canal to the petrous carotid canal, (3) laterally through the
pterygomaxillary fissure into the masticator space, (4) superiorly through the
inferior orbital fissure into the orbital apex, with subsequent intracranial
extension via the superior orbital fissure, and (5) inferiorly through the
pterygopalatine canal into the oral cavity.
Features that constitute intracranial extension include the presence of
meningeal involvement (appearing as nodular enhancement), soft tissue masses
within the middle and/or posterior cranial fossa, as well as evidence of
perineural spread. Direct invasion of the brain is rare at diagnosis
. There are multiple routes into the cavernous sinus, including
perivascular extension along the horizontal portion of the internal carotid
artery through the foramen lacerum (Figure 7A, B), perineural extension along
the V3 through the foramen ovale(Figure 7C), as well as direct extension from
the orbital fissures or through the skull base . With cavernous sinus
involvement, cranial nerves III, IV, V1, V2, and VI are vulnerable to tumor
invasion, often resulting in multiple cranial nerve palsies. True perineural
spread; however, is uncommon in the pre-treatment setting . Cranial nerve
invasion is associated with a higher rate of distant metastases and decreased
survival . Post-contrast T1-weighted images with fat saturation are used to
assess for cranial nerve involvement, especially for the maxillary nerve (V2)
along the foramen rotundum and the mandibular nerve (V3) in the foramen ovale (Figure 8). Nerve involvement is suspected
when abnormal enlargement or enhancement of the nerves or obliteration of fat
pads adjacent to neurovascular foramina is observed. Contrast-enhanced images
show perineural disease extension and cavernous sinus involvement as asymmetric
nodular thickening and abnormal enhancement. A late sign is expansion of the
bony canals in which these nerves travel.
Disease spread via the inferior orbital fissure represents the most
common route of orbital invasion. NPC can also extend into masticator space,
where the medial and lateral pterygoid muscles, temporalis muscle,
infratemporal fat, as well as the mandibular nerve will all be vulnerable to
tumor infiltration. From the masticator space, NPC can also gain access to the
intracranial cavity and cavernous sinus via direct extension through the floor
of the middle cranial fossa or via the foramen ovale (Figure 9).The hypopharynx, which is the most inferior site included in
the TMN staging system, is rarely involved at diagnosis. NPC has a tendency to
spread superiorly rather than inferiorly .
Figure 7A, B, C: Two coronal T1 images (7A, B) shows a left sided NPC
with extension superiorly into the left foramen lacerum (arrows in 7A). Also
note the abnormal signal within the adjacent left aspect of the clivus. Image
7B shows that the tumor is also involving the left cavernous sinus (*). Coronal
T2 image in another patient (7C) shows a left NPC that has extended into the
ipsilateral masticator space (MS) with subsequent perineural tumor spread along
an enlarged V3 , through foramen ovale and into the cavernous sinus (arrows
Figure 8. Axial contrast enhanced T1 image shows enhancing tumor within
the left orbit (arrows). The patient has an NPC which involved the cavernous sinus
with subsequent tracking along foramen rotundum into the pterygopalatine fossa
and the inferior orbital fissure.
Figure 9. Coronal contrast enhanced T1 weighted shows a large right NPC
that has infiltrated the right masticator space (MS) with contiguous extension
superiorly onto the cavernous sinus, right sphenoid sinus (Sph) and along the
floor of the middle cranial fossa.
Regional Lymph Nodes (N)
Up to 90% of NPC cases will present with lymph node metastases at
presentation. Thus, only 10% to 40% of patients will present without nodal
disease (N0) [19, 38]. Positive nodal disease is associated with
increased risk of local recurrent and distant metastases . NPC generally
follows a sequential pattern of nodal spread, beginning with involvement of
retropharyngeal lymph nodes (RPN) occurring before other nodal groups along the
internal jugular chain (chain II to IV), spinal accessory chain (Va and Vb), as
well as supraclavicular nodes. Although the RPN are generally considered the
first echelons of metastatic spread, studies have shown that this is not true
in all cases [30, 39-41]. The RPN may be bypassed in up to 19% of cases .
In addition, Ng et al. also reported skip metastases in the lower neck
lymph nodes and the supraclavicular fossa in 7.9% of cases, and distant
metastases to thoracic and abdominal nodes in 3-5% of cases . Level IIa and
b nodes are the most common site of non-retropharyngeal nodal involvement .
Unlike other head and neck squamous cell carcinomas, nodal disease in NPC is
more frequently bilateral.
Stage N1 refers to the presence of unilateral metastasis in cervical
lymph node(s) and/or unilateral or bilateral retropharyngeal lymph nodes. In
both cases, the diameter is less than 6 cm in the greater dimension. Nodes
greater than 3 cm in size are generally considered “nodal masses”
and are indicative of confluent nodes. Stage N2 refers to bilateral nodal
disease involving cervical lymph node(s) that are also less than 6 cm in the
greatest dimension. Unlike other carcinomas in the neck, N2 is not further
divided into substages. In both N1 and N2, disease is restricted to above the
supraclavicular fossa, which is defined by three points: (1) the superior
margin of the sternal end of the clavicle, (2) the superior margin of the
lateral end of the clavicle, and (3) the point where the neck meets the
shoulder. Supraclavicular nodes refer to all lymph nodes seen on the same axial
images as a portion of the clavicle, and include caudal portions of levels IV
and Vb nodes. Nodal disease greater than 6 cm in diameter signifies stage N3a
disease, while involvement of supraclavicular fossa lymph nodes denotes stage
While distinguishing between the primary tumor mass and adjacent RPN is
best assessed with MRI, cervical lymph nodes can be evaluated accurately with
both MRI and CT . T2-weighted imaging with fat saturation shows nodes as
bright structures in the posterior cervical fat. The higher resolution of
CT facilitates the visualization of neck adenopathy, as well as nodal necrosis
and extracapsular extension, with the latter manifesting as loss or
irregularity of the nodal margins, and/or haziness of the adjacent fat .There
are several imaging features suggestive of positive nodal disease, including
large size (generally, >1.5 cm for levels I and II, >1 cm for levels
IV-VII, and >5 mm for retropharyngeal lymph nodes in the shortest transaxial
dimension), 3 or more lymph nodes borderline in size, rounded nodes with loss
of the normal fatty hilum, and necrosis [35, 38]. If identified, necrosis is
considered 100% specific. Necrosis is visualized as a hypointense area on
T1-weighted images with rim enhancement on contrast administration, and a
hyperintense area on T2-weighted images. On CT, necrosis is seen as a focal
area of hypoattenuation with or without rim enhancement. Patients with nodes
showing necrosis and extranodal spread have a very poor prognosis with a 50%
decreased 5-year survival rate .
The M stage of NPC is similar to that of other malignancies, whereby M0
signifies the absence of distant metastasis and M1 refers to the presence
of such disease. NPC has the highest incidence of distant metastasis among head
and neck cancers, with a rate as high as 11% at diagnosis [34, 44]. Distant
metastases most commonly affect bone, lung and liver .Thus, bones and lung
apices should be evaluated for tumor involvement in head and neck MRI studies,
especially in patients with risk factors such as metastatic cervical nodes
extending to the supraclavicular fossa (stage N3).
The exact method for the evaluation of distant metastasis will vary from
institution to institution. Imaging options include bone scintigraphy,
chest x-ray, CT of the thorax, abdomen and pelvis, and PET/CT. Studies have
shown fluorodeoxyglucose PET/CT imaging to have a higher sensitivity and
specificity in detecting
distant metastases [11, 22, 24, 25, 46-50].
Nasopharyngeal carcinoma is a relatively rare neoplasm that most commonly
arises in the lateral pharyngeal recess and has a tendency toward local
invasion and spread to surrounding structures. Cervical lymphadenopathy is also
very common at presentation. Diagnosis of NPC can be made on
endoscopically-guided biopsy; however, cross-sectional imaging, particularly
MRI, plays a key role for accurate assessment of tumor volume and extent. A
thorough understanding of the anatomy of the nasopharynx and surrounding
structures, as well as the natural history of the disease is essential, as NPC
has a propensity towards early infiltration into deeper neck spaces and has
well-defined patterns of spread. Staging of NPC is based on the most up-to-date
2010 AJCC guidelines. MRI is currently the best tool for assessing tumor extent
under the current staging system, while PET/CT is emerging as the most accurate
modality for assessing distant metastases andtumor recurrence.
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