Tumour budding in solid cancers

Tumour budding is an emerging prognostic biomarker in colorectal cancer (CRC) and other solid cancers. Tumour buds are usually defined as isolated single cancer cells or clusters of up to four cancer cells located at the invasive tumour front. The prognostic value of tumour budding is now supported by a large body of evidence, whereas the utility of this phenotype as a predictive biomarker remains under investigation. The application of tumour budding indices in clinical practice requires a standardized scoring system that can be tailored to specific tumour types and clinical scenarios. In the context of CRC, tumour budding can be assessed according to the method agreed at the International Tumour Budding Consensus Conference (ITBCC) in 2016. Using the ITBCC scoring system, tumour budding is an independent predictor of lymph node metastasis in patients with pT1 CRC and of unfavourable survival in patients with stage II colon cancer. Regardless of the clinical scenario or tumour type, the assertion that 'the more tumour buds, the worse the clinical outcome' applies. In this Review, we provide an overview of tumour budding in solid cancers, highlighting the molecular and biological aspects of this phenomenon, including its associations with epithelial-mesenchymal transition and features of the tumour microenvironment. We also describe the available evidence demonstrating the value of tumour budding as a biomarker across various solid cancers. Tumour budding is hypothesized to reflect the invasive and metastatic capacities of cancers and is accordingly associated with unfavourable patient outcomes. Herein, Lugli and colleagues describe the pathobiological characteristics of this phenomenon, including its associations with epithelial-mesenchymal transition and features of the tumour microenvironment, and review the evidence demonstrating the value of tumour budding as a prognostic biomarker across various solid cancers.

Automated summary

Tumour budding serves as an emerging prognostic biomarker in colorectal cancer and other solid cancers, with its predictive accuracy being widely supported by evidence. The standardized scoring system agreed upon at the International Tumour Budding Consensus Conference allows for an independent prediction of pathological features and unfavorable survival outcomes in patients.