The usefulness of FDG-PET/CT in the diagnosis of head and neck squamous cell carcinoma (HNSCC) of unknown primary with cervical lymph node metastasis

Abstract

Introduction: Carcinoma of unknown primary is uncommon, estimated to represent only 3–5% of all head and neck cancers.

Aim: The aim of our study was to estimate the role of FDG-PET/CT in the detection of the occult primary tumor in patients with histologically proven squamous cell carcinoma and cervical lymph node metastasis.

Materials and Methods: We retrospectively reviewed a total of 18 patients with unknown primary and head and neck squamous cell carcinoma (HNSCC) presented as cervical lymph node metastasis. They were referred to the Department of Nuclear Medicine in the period 2015–2017. All patients presented fine-needle biopsy proven squamous cell carcinoma metastasis of the neck lymph nodes. The patients underwent PET/CT for detection of unknown primary head and neck cancer after endoscopic/physical examination and computer imaging (contrast-enhanced CT of neck, thorax/abdomen).  The final results were obtained from the histopathologic reports of tissue samples from anatomical regions suspected for primary tumor, additional imaging exams and clinical follow-up data.

Results: There were FDG-PET/CT identified sites suggestive of primary tumor location in 12 patients. Subsequent directed biopsy of these sites yielded positive results in 11 cases (61%): hypopharynx—1 (9%), nasopharynx—3 (27%), oropharynx—5 (42%), larynx—1 (9%), skin of the face—1 (9%). Тhere was 1 false positive result (5.5%). Six out of 18 patients (33%) remained without evidence of a primary tumor.  In 1 case (5.5%) we did not reveal any pathology within the localizations indicated by FDG-ET/CT on directed biopsy.  In 1 case (5.5%) we obtained histological confirmation of neoplasm despite the negative results of the PET/CT scan. FDG-PET/CT had a sensitivity of 92%, a specificity of 83%, a positive predictive value of 92%, a negative predictive value of 83%, and accuracy of 89% in the identification of head and neck squamous cell carcinoma of unknown primary with cervical lymph node metastasis.

Conclusion: Non-invasive FDG-PET/CT offers a great likelihood of successfully identifying the location of head and neck squamous cell carcinoma of unknown primary with cervical lymph node metastasis.