Metastasis and the associated loss of function of vital organs in the course of the disease is one of the main causes of death in head and neck cancer patients. An earlier and more reliable determination of metastasis and recurrence than currently obtained by common imaging methods could improve therapy and therefore the prognosis of head and neck cancer patients. The detection of tumor cells, which circulate in the blood of cancer patients, known as circulating tumor cells and those that can be found in the bone marrow, called disseminated tumor cells (DTC) provides a diagnostic source especially for those patients at high risk of locoregional recurrence or distant failure. Circulating tumor cells (CTC) have been identified as a prognostic factor in different solid tumors. In head and neck squamous cell carcinoma, there are data for a similar prognostic relevance. The methods of detection of CTC/DTC, the role in diagnosis and follow-up in head and neck cancer are summarized in this review. Furthermore, the future technical and clinical challenges to be addressed to establish CTC/DTC in clinical routine are being critically discussed.
