Investigations
1st investigations to order
nasopharyngoscopy
Test
Initial diagnostic evaluation of choice to identify the primary tumour if patients present with a suspicious neck mass or with nasal and aural symptoms, especially if the patient is from southern China or southeast Asia (which have an especially high incidence of nasopharyngeal cancer [NPC]).[2][19][22] NPC most commonly arises from the fossa of Rosenmüller.
It is important to outline the extent of the tumour as subtle mucosal extension may not be easily seen on imaging.
Result
Lesion observed on endoscopy, most commonly arising from lateral pharyngeal recess (fossa of Rosenmüller)
tumour biopsy
Test
A diagnosis of nasopharyngeal cancer (NPC) is best made with endoscopic-guided biopsy of the primary tumour.[2] If a diagnosis is made from a neck nodal metastasis (e.g., primary tumour not visible on endoscopy), fine-needle aspiration is preferred.[22] Incisional neck biopsy or nodal dissection should be avoided.[2]
NPC in endemic regions is almost ubiquitously associated with Epstein-Barr virus (EBV) and has a more favourable prognosis. It is characterised by malignant epithelial cells of squamous origin but lack keratinisation and have a rich lymphocytic infiltrate.
Non-keratinising NPC is subdivided into differentiated (formerly WHO type II) and undifferentiated (formerly WHO type III) subtypes. Keratinising squamous cell carcinoma (formerly WHO type I) is a subtype of NPC that is more common in non-endemic regions.[2] Compared with non-keratinising NPC, keratinising NPC is less associated with EBV and more with cigarette smoking.
Result
Tumour cells identified
MRI of the nasopharynx, skull base, and neck (to clavicles)
Test
MRI with or without contrast is more sensitive than CT in detecting subtle mucosal thickening, parapharyngeal, skull base, and cranial nerve involvement, which all impact staging.[25]
Staging for prognostication is determined by the local extent of the cancer within the site of origin (T) and the degree of metastatic involvement of the regional lymph nodes (N).
Result
Identifies suspicious lesions and metastatic disease
18F-FDG-PET/chest CT
Test
PET/chest CT detects more distant metastases than conventional staging in patients with nasopharyngeal cancer.[19][26] Staging for prognostication is determined by the presence or absence of distant metastatic disease (M).
Bone is the most common site for metastasis, followed by lung and liver.
Result
Identifies metastatic disease
Investigations to consider
plasma Epstein-Barr virus (EBV) DNA
Test
Plasma Epstein-Barr virus (EBV) DNA can be used as a biomarker to predict prognosis and detect subclinical recurrence.[2][19][23]
Checking pre-treatment plasma EBV DNA levels may improve prognostic performance.[27]
Result
High plasma EBV (>4000 copies/mL) is associated with a higher chance of distant metastasis
Epstein-Barr virus-encoded RNA in situ hybridisation (EBER ISH)
Test
Not routinely performed on tumour tissues in endemic countries, but it is useful in establishing a diagnosis in cases of occult primary tumours.
Result
Positive studies show staining in the nuclei of the EBV-infected cells
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