Objective: To assess the efficacy of various diagnostic modalities in detecting occult primary tumor location.
Design: Retrospective medical record study.
Setting: Academic head and neck oncology practice.
Patients: A total of 183 consecutive patients with metastatic carcinoma of the neck from an unknown primary tumor during a 10-year period, after exclusion of those with previous history of head and neck cancer, a primary tumor site evident on physical examination, or primary tumors of the neck.
Main outcome measures: Identification of primary tumor location by various imaging modalities and panendoscopy with directed biopsies.
Results: Primary tumor location was identified in 84 patients (45.9%). Preoperative imaging (computed tomography [CT], magnetic resonance imaging, positron emission tomography [PET], and/or PET-CT fusion scan) identified sites suggestive of primary tumor location in 69 patients. Subsequent directed biopsy of these sites yielded positive results in 42 cases (60.9%). The rate of successful identification of a primary tumor for each of the imaging modalities was as follows: CT scan of the neck, 14 of 146 patients (9.6%); magnetic resonance imaging of the neck, 0 of 13 patients (0%); whole-body PET scan, 6 of 41 patients (14.6%); and PET-CT fusion study, 23 of 52 patients (44.2%) (P = .001). The highest yield in identifying primary tumor sites was obtained in patients who had undergone PET-CT plus panendoscopy with directed biopsies with or without tonsillectomy: 31 of 52 patients (59.6%).
Conclusion: Diagnostic workup including PET-CT, alongside panendoscopy with directed biopsies including bilateral tonsillectomy, offers the greatest likelihood of successfully identifying occult primary tumor location.