Cervical lymph node metastases of squamous cell carcinoma of unknown origin: the diagnostic value of FDG PET/CT and clinical outcome

Eur Arch Otorhinolaryngol. 2017 Feb;274(2):1015-1019. doi: 10.1007/s00405-016-4318-5. Epub 2016 Sep 26.


FDG PET/CT is perceived as a valuable diagnostic tool in addition to the standard diagnostic workup for patients with isolated neck lymph nodes of squamous cell carcinoma of unknown primary (SCCUP). For patients with SCCUP intended for primary radiotherapy, we hypothesize that the previously reported FDG PET/CT detection rates are too high. From 2008 to 2015, 30 SCCUP patients were examined with FDG PET/CT. The objective of the FDG PET/CT examination was twofold: (1) improve the radiotherapy target definition, and (2) identify the primary cancer. Before the FDG PET/CT, the patients had been through a standard workup consisting of CT of the neck and chest, examination with flexible endoscopy with patient awake, panendoscopy and examination under general anesthesia, tonsillectomy and sometimes blind sampling biopsies, and MRI (floor of the mouth). All FDG PET/CTs were performed applying a flat table, head support and fixation mask as part of the radiotherapy treatment planning. Diagnostic CT with contrast was an integrated part of the PET/CT examination. Only 1/30 patients (cancer of the vallecula) had their primary cancer detected by FDG PET/CT. In addition, a non-biopsied patient with high uptake in the ipsilateral palatine tonsil was included, giving a detection rate of ≤7 % (95 % CI 2-21 %). In this retrospective study, we found that the FDG PET/CT detection rate of the primary for SCCUP patients is lower than previously reported. It is questionable whether FDG PET/CT is necessary for these patients when improved, advanced workup is available.

Keywords: 18F-FDG; Cancer of unknown primary; Cervical lymph node metastases; Head and neck cancer; Positron emission tomography.

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Carcinoma, Squamous Cell / diagnosis*
  • Carcinoma, Squamous Cell / secondary
  • Female
  • Fluorodeoxyglucose F18 / pharmacology*
  • Head and Neck Neoplasms / diagnosis*
  • Head and Neck Neoplasms / secondary
  • Humans
  • Lymph Nodes / diagnostic imaging*
  • Lymphatic Metastasis
  • Male
  • Middle Aged
  • Neck
  • Neoplasms, Unknown Primary*
  • Positron Emission Tomography Computed Tomography / methods*
  • Prognosis
  • Radiopharmaceuticals / pharmacology
  • Retrospective Studies


  • Radiopharmaceuticals
  • Fluorodeoxyglucose F18