[Contribution of 18-F-FDG PET for detection of head and neck carcinomas with an unknown primary tumor]

To evaluate the usefulness of fusioning positron emission tomography with computed tomography (PET/CT) for the detection of head and neck carcinomas of unknown primary.

This prospective study included 20 patients with cervical lymph node of squamous cell carcinoma of unknown primary after standard initial workup (nasofibroscopy and CT scan of the chest and head and neck). Patients underwent PET/CT and panendoscopy of the upper airways and upper digestive tract with PET/CT directed biopsies. The follow-up was 6 months minimum in all patients.

A potential primary tumor was found in 10 of the 20 cases and confirmed by histology in 7 cases (3 bases of tongue, 1 tonsillar pillar, 1 vallecula, 1 tonsillar fossa, 1 piriform sinus). Four of these seven patients presented a normal endoscopy (diagnosis was made with submucosal PET/CT directed biopsies). PET/CT was normal in 10 of 20 cases with 3 false negatives. The sensitivity of PET/CT was 70%, the specificity was 70% and the accuracy was 70%.

PET/CT seems to be of interest in the detection of head and neck carcinoma of unknown primary. PET/CT detected 15% of unknown primary tumors with treatment-related implications.