Best Imaging Modality to Detect Cervical Metastases of Unknown Primary Tumors

Hossein Jadvar, MD, PhD, MPH, MBA


April 09, 2015

Detection of Occult Primary Tumors in Patients with Cervical Metastases of Unknown Primary Tumors: Comparison of (18)F FDG PET/CT With Contrast-Enhanced CT or CT/MR Imaging—Prospective Study

Lee JR, Kim JS, Roh JL, et al
Radiology. 2015;274:764-771


The aim of this prospective study was to compare the diagnostic performances of fluorodeoxyglucose (FDG) PET/CT and contrast-enhanced CT (CECT), alone or in combination with MRI in 56 patients with head and neck squamous cell carcinoma (SCC) with cervical adenopathy but no localization of the primary tumor after panendoscopic evaluation. Primary tumors were eventually detected in 55% of patients; most tumors were located in the palatine tonsils, and only a few were in the hypopharynx, nasopharynx, or base of the tongue.

The sensitivities of FDG PET/CT, combined CECT/MRI, and CECT in detection and localization of the primary head and neck tumor were 69%, 41%, and 16%, respectively. The specificities of FDG PET/CT, combined CECT/MRI, and CECT were 88%, 59%, and 76%, respectively, and they did not statistically differ from one another.

FDG PET/CT detected the primary tumor in 50% of false-negative CECT/MRI findings. FDG PET/CT also detected previously unknown distant metastases in one case and synchronous tumors in two cases.


The primary tumor may not be detected in 2%-9% of patients with head and neck SCC lymphadenopathy despite extensive work-up that includes panendoscopy and tissue sampling at prescribed sites.[1] Previous retrospective studies that included heterogeneous patient cohorts and reference standards suggested a major role for FDG PET/CT in this clinical setting.[2]

This prospective investigation from South Korea that incorporated well-defined inclusion and exclusion criteria and image-guided tissue biopsy as reference standard arrived at a similar conclusion—that FDG PET/CT might have a major role in the identification and localization of occult head and neck primary tumors. The CT that accompanied combined PET/CT was used for attenuation correction with the following parameters: 100 mA, 120 kV, 5-mm section thickness, 0.75 mm per gantry rotation, and no intravenous contrast. The CECT parameters, however, were 200 mA, 120 kV, 3-mm section thickness, and use of intravenous contrast. MRI was performed using a 1.5-T unit with 3-mm section thickness in the axial and sagittal and coronal planes.

As hybrid PET/MRI systems become more commonplace, it is reasonable to anticipate that identification of the head and neck primary tumor may become an important clinical indication for this combined imaging modality. Whether the improved diagnostic performance of FDG PET/CT can make an impact on patient outcomes will need further research.



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