Incidental uptake of fluorodeoxyglucose in the Waldeyer’s ring and risk of oropharyngeal malignancy

Abstract

Purpose Fluorodeoxyglucose (FDG) positron emission tomography (PET) is increasingly used to diagnose and stage malignancy. The aim of this article is to investigate the significance of incidental FDG uptake in the Waldeyer’s ring and to assess its value in predicting clinically occult oropharyngeal malignancy. Methods All FDG-PET/CT scans performed in Imperial College NHS Foundation Trust, UK between January 2012 and November 2018 were included. Patients with known or suspected oropharyngeal malignancy or lymphoma were excluded. Minimum follow-up was 12 months. Results A total of 724 scans revealed oropharyngeal uptake of FDG. Of these, 102 were included in the study. Most patients (62.1%) were scanned as part of staging for other malignancies. Oropharyngeal FDG uptake was asymmetrical in 57.3% of the cases. Uptake was more common in the tonsils (56.3%), followed by the tongue base (31.1%) and both sites (12.6%). In 41.7% of reports, appearance was described as likely physiological; however, 52.4% of reports advised direct visualisation, clinical correlation or ENT opinion. Only 24.3% (25/102) of patients were referred and seen by ENT, 14.6% (15/102) of which had an interval PET scan and 8.7% (9/102) proceeded to tissue diagnosis. There was one oropharyngeal cancer identified and one unexpected metastasis from esophageal cancer. Conclusion Incidental uptake on PET/CT in the oropharynx is common. However, malignancy is rare (1.9%) and, when present, is associated with high SUVmax and asymmetrical uptake. Imaging results must be correlated clinically. These patients should be seen by an ENT specialist yet most may not require further investigations.

Risk of malignancy in incidental oropharyngeal lesions exhibiting fluorodeoxyglucose uptake which proceed to tissue biopsy

“…Existing guidelines and reviews have examined the broader literature pertaining to incidental PETavid lesions. 2,11 Up to 11.7% of incidental lesions detected during the workup of an existing head and neck malignancy are located in the head and neck, and result in delays to treatment initiation and worsens overall survival outcomes. 18 In this comprehensive search of three major hospital databases, there were two unexpected malignancies identified in 31 patients undergoing surgery for PET-avidity in the oropharynx.…”

“…12 One study examining generalized uptake in Waldeyer's Ring in 102 patients undergoing surveillance PET for other malignancies noted only 1 event of metastatic oropharyngeal cancer. 11 Similarly, one retrospective study performed on surveillance PET for 592 patients with known lung cancer demonstrated only 10 patients with uptake in the oropharynx, of which there was one case of oropharyngeal osteosarcoma. 13 Furthermore, even in patients with pre-existing tonsillar malignancy, the significance of PET-avidity of the contralateral tonsil is uncertain.…”

“…9,10 Asymmetrical tonsillar standardized uptake value maximum value (SUV max ) suggests an increased risk of a malignant process. 2,11 However, incidental uptake does not necessarily correlate to malignancy. In addition to pathological causes of PET avidity, physiological uptake in the head and neck is common, particularly with reactive uptake in Waldeyer's ring in response to acute inflammatory processes.…”

The radiological unknown primary of the head and neck: Recommendations for imaging strategies based on a systematic review

“…32 Minor asymmetrical uptake is frequently seen in non-malignant tonsils. 32,33 There are no studies on the role of 18F FDG PET-CT specifically in the assessment of the contralateral neck in HNSCCUP. A meta-analysis of the role of 18F FDG PET-CT in detecting nodal metastasis in patients with HN SCC showed a sensitivity of 79% and specificity was 86%.…”

“…However, some malignant tonsils have normal FDG uptake; therefore, PET‐CT should not be used to exclude tonsillar cancer. 32 Minor asymmetrical uptake is frequently seen in non‐malignant tonsils 32,33 …”