Tumour budding in head and neck squamous cell carcinoma - a systematic review

Tumour budding is a specific type of invasive growth in carcinomas characterized by invading single tumour cells or small clusters of tumour cells (<5 cells) at the invasive front (IF). It has been documented in numerous publications during the past few decades, but its value as a prognostic marker in head and neck squamous cell carcinoma (HNSCC) has been analysed only recently. In this review we aimed to address the question of whether or not tumour budding has an impact upon the progression and prognosis of HNSCC. We systematically reviewed the databases of PubMed, Scopus and Web of Science for articles that studied tumour budding in squamous cell carcinoma of the head and neck region. The search was limited to articles published in the English literature before March 2014. A total of 122 hits were retrieved; however, only five reports met the inclusion criteria. The findings of these reports suggested a strong association between tumour budding and tumour progression, in addition to strong correlation with patient prognosis. Standardization of the scoring method and the risk stratification cut-off point is necessary before the inclusion of tumour budding in pathological reports during daily practice.