Head and Neck ImagingOccult primary tumour, head and neck
A patient with
carcinoma presenting as a single or multiple neck adenopathies, in whom no primary
tumour is detected after careful clinical and radiological work-up, is said to have an
occult primary
tumour. About 5% of head and neck cancers present in this way. As neck carcinomas follow particular anatomical routes through the lymphatic drainage, the localization of the adenopathies may give a clue to the location of the primary
tumour. The most likely sites for an
occult primary
tumour are nasopharynx, tonsil, pyriform
sinus and tongue base. The detection rate of clinically
occult tumours with
CT or
MRI is about 15-20%. Such
occult tumours are only detectable using primarily anatomically based imaging methods if they distort deep anatomical planes. Any asymmetry ipsilateral to the site of nodal involvement is to be regarded with suspicion, and should be biopsied (
Fig.1). Imaging should in any case be performed before
endoscopy with multiple (speculative) biopsies, as this procedure may cause tissue changes mimicking an early
tumour. Preliminary data regarding the value of
PET and
SPECT imaging in this setting are promising. Detection of the
occult primary
neoplasm influences therapy, as it can be tailored to the discovered primary (surgical resection and/or tailored radiation treatment).
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Axial contrast-enhanced CT images of neck.
a. Multiple parajugular adenopathies are seen on the left, lymphatic metastases of squamous cell carcinoma.
b. Subtle infiltration of the left Rosenmuller's fossa is seen (arrowheads, b). This was proven to be the primary tumour.
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Occult primary tumour, head and neck, Fig.1 (a) | | Occult primary tumour, head and neck, Fig.1 (b) | |