Head and neck cancer is one of the most common malignancies. Currently, it has a poor
prognosis and significant mortality as the majority of malignancies present in later stages. Early diagnosis
affords early intervention and the best chance of cure. However, the current gold standard for diagnosis
largely depends on histopathology via an invasive procedure, tissue biopsy. The processing of
biopsy material also inevitably leads to diagnostic delay and the possibility of taking an unrepresentative
sample. Recently, there has been significantly increasing interest in the use of spectroscopy (e.g.,
fluorescence, elastic scattering, and Raman spectroscopy) and other optical systems to provide an
early, real-time, non-invasive, and in situ diagnosis. Such diagnosis is based on the fact that the optical
spectrum derived from any tissue reveals information about the histological and biochemical characteristics of that tissue.
These optical systems have not only a role in cancer detection but also in treatment through guided biopsy, surgical margin
assessment, and the monitoring of therapeutic drugs. However, our literature search is limited only to clinical diagnosis
and only to the clinical trials published within recent 15 years (in 2000-2014). In this review, we will discuss and
summarize the progress and new findings from recent clinical trials using these optical systems in the diagnosis of head
and neck cancer.