Title: Lymph Node Metastases from an Unknown Head and Neck Primary Site: Evaluating the Diagnostic Work-up
Abstract: Despite an adequate diagnostic workup, 2% to 3% of neck node metastases from a primary head-and-neck tumor cannot be detected. There is no general consensus on the optimal diagnostic workup, and its timing, for carcinomas of an unknown primary (CUP). The purpose of our study is to describe the detection rate and identification of the location of the primary after a conventional workup and panendoscopy with or without a tonsillectomy and with or without an 18-F-FDG positron emission tomography (PET) or PET/computed tomography (CT) scan. We retrospectively reviewed the charts of 236 patients treated between June 1983 and December 2008 who were diagnosed as having CUP after a conventional workup that included physical examination (PE), mirror and fiber-optic examination, CT, and/or magnetic resonance imaging (MRI) of the head and neck, and for whom there was no identified primary tumor. Panendoscopy was subsequentely performed at least once in all patients. 18-F-FDG PET or PET/CT was obtained in 21 cases. A tonsillectomy was performed in 79 patients, 7 of which were bilateral. Patients with a low-neck or supraclavicular tumor location were not considered for this study since they had a primary most likely localized below the clavicles. Only patients with squamous cell carcinomas were included in the study. A primary lesion was found in 126 patients (53.3%), 6 of whom had 2 synchronous primaries. Locations were: tonsillar fossa, 59 patients (44.7%); base of tongue, 58 patients (43.9%); pyriform sinus, 10 patients (7.6%); pharyngeal wall, 3 patients (2.3%); nasopharynx, 1 patient (0.75%); and supraglottic larynx, 1 patient (0.75%). Detection rate was significantly lower in patients with no suspicious findings on workup and a negative physical exam CT and/or MRI (29.2%), as compared to those with at least 1 suspicious finding (64.0%). FDG-PET or PET/CT was performed in 21 patients and was positive in 5 of 21 patients (23.8%); in 3 patients a biopsy-proven primary was confirmed (14.3%). In 35 of 79 patients (44.3%) who underwent a tonsillectomy, a primary was found. Multivariate analysis revealed that clinical suspicion on PET and CT and/or MRI were significantly-related with the identification of the primary (p = 0.0234 and p < 0.0001, respectively). The most common primary sites for CUP are the tonsillar fossa (44.7%), base of tongue (43.9%), and pyriform sinus (7.6%). Panendoscopy with biopsy of suspicious sites remains the mainstay of the diagnostic workup. Metabolic studies do not appear to add valuable information to the detection rate of the primary site. An ipsilateral tonsillectomy should be performed, particularly if there are suspicious signs on PET and/or radiologic studies.