Tumor budding is defined as a single tumor cell or a cell cluster of up to 4 tumor cells, it is an independent predictor of lymph node metastasis in pT1 colorectal cancer and an independent predictor of survival in stage II colorectal cancer, and it should be taken into account along with other clinicopathologic factors in a multidisciplinary setting [1].
Tumor budding is counted on hematoxylin-eosin.
Intratumoral tumor budding in colorectal cancer has been shown to be related to lymph node metastasis and it should be included in guidelines/protocols for colorectal cancer reporting [1].
Tumor budding and tumor grade are not the same.
Tumor budding is graded according to its number in a microscopic field with a ×20 objective lens (0.785 mm2) in the hotspot. Tumors with less than five, five to nine, and 10 or more budding foci as classified as grades BD1, BD2, and BD3, respectively [2]. Category BD3 is subclassified as BD3a for tumors with 10 to 19 and BD3b for those with 20 or more budding foci in the hotspot (in a field of 0.785 mm2) at the invasive front [2].
Bibliographic references:
[1] Cho SJ, Kakar S. Tumor Budding in Colorectal Carcinoma: Translating a Morphologic Score Into Clinically Meaningful Results. Arch Pathol Lab Med. 2018;142(8):952-957. Available at: https://doi.org/10.5858/arpa.2018-0082-RA.
[2] Ueno H, et al. Prospective Multicenter Study on the Prognostic and Predictive Impact of Tumor Budding in Stage II Colon Cancer: Results From the SACURA Trial. J Clin Oncol. 2019;37(22):1886-1894. Available at: https://doi.org/10.1200/JCO.18.02059.
