The detection of unknown primary tumors in patients with cervical metastases by dual-head positron emission tomography.

A dilemma may occur in relation to patients with cervical metastases appearing as the first sign of malignancy in the head and neck region. In these patients, the location of the involved lymph nodes may indicate the location of the primary tumor. However, in two or three per cent of the patients, the primary tumor cannot be identified in the diagnostic workup. The aim of the present study was to investigate the possibility of identification of primary tumors in patients with cervical metastases of unknown origin, by the use of 2-(fluorine-18)fluoro-deoxy-D-glucose (FDG) dual-head positron emission tomography (PET). Ten consecutive patients with a cervical metastases of unknown origin were studied with FDG, using a dual-head PET camera. After the injection of 185 MBq (5 mCi) of FDG, images were performed of the head, neck and chest. In addition, endoscopy and biopsies were carried out with knowledge of the PET study. In patients in whom a primary tumor could not be identified, a follow-up of at least 6 months was used as a control. In five out of 10 patients a primary tumor was identified by FDG-PET. In one patient multiple sites of uptake were seen, and this was found to be consistent with non-Hodgkin lymphoma. In five patients, additional sites of increased uptake were found, these being consistent with unknown metastatic disease. Finally, in six patients, the initial treatment plan was changed due to the PET result in five of them. In one patient, the primary tumor was resected revealing a lesion with a diameter of 6 mm. The detection of FDG in patients with cervical metastases of unknown origin by the use of a dual-head PET camera is a valuable diagnostic tool in the identification of primary lesions.