Tumor budding in colorectal cancer revisited: results of a multicenter interobserver study

Abstract

Tumor budding in colorectal cancer (CRC) is recognized as a valuable prognostic factor but its translation into daily histopathology practice has been delayed by lack of agreement on the optimal method of assessment. Within the context of the Swiss Association of Gastrointestinal Pathology (SAGIP), we performed a multicenter interobserver study on tumor budding, comparing hematoxylin and eosin (H&E) with pan-cytokeratin staining using a 10 high power field (10HPF) and hotspot (1HPF) method. Two serial sections of 50 TNM stage II-IV surgically treated CRC were stained for H&E and pan-cytokeratin. Tumor buds were scored by independent observers at six participating centers in Switzerland and Austria using the 10HPF and 1HPF method on a digital pathology platform. Pearson correlation (r) and intra-class correlation coefficients (ICC) comparing scores between centers were calculated. Three to four times more tumor buds were detected in pan-cytokeratin compared to H&E slides. Correlation coefficients for tumor budding counts between centers ranged from r = 0.46 to r = 0.91 for H&E and from r = 0.73 to r = 0.95 for pan-cytokeratin slides. Interobserver agreement across all centers was excellent for pan-cytokeratin [10HPF: ICC = 0.83 and 1HPF: ICC = 0.8]. In contrast, assessment of tumor budding on H&E slides reached only moderate agreement [10HPF: ICC = 0.58 and 1HPF: ICC = 0.49]. Based on previous literature and our findings, we recommend (1) pan-cytokeratin staining whenever possible, (2) 10HPF method for resection specimens, and (3) 1HPF method for limited material (preoperative biopsy or pT1). Since tumor budding counts can be used to determine probabilities of relevant outcomes and as such more optimally complement clinical decision making, we advocate the avoidance of cutoff scores.

Tumour Budding and Survival in Stage II Colorectal Cancer: a Systematic Review and Pooled Analysis

“…They calculated that agreement among 6 different participating obsever in a multicentre study is higher for the first method. So, they suggested that tumour budding counts should avoid any cut-off scores and should be based on IHC (pan-citokeratin staining) [43]. Horcic et al in particular underline that scoring tumour buds in 10 densest high-power fields represent a promising method to identify stage II patients at high risk for recurrence, is highly reproducible, accounts for heterogeneity and has a strong predictive value for adverse outcome [44].…”

MicroRNA-200b is downregulated in colon cancer budding cells

“…According to this method, the number of buds is counted in ten fields of view at a 40x objective [12, 13]. Cases with an average of ≤ 10 buds were designated as low budding, >10 as high budding [13].…”

Recommendations for reporting tumor budding in colorectal cancer based on the International Tumor Budding Consensus Conference (ITBCC) 2016

“…field" and "10 high power field" methods) [11][12][13][14][15][16]18 . Counting across multiple fields has the advantage of being more representative of the entire invasive front, and there is also some evidence of improved inter-observer agreement using this approach [11][12][13][14][15][16]18,45 . On the other hand, counting multiple fields may "dilute" the final (mean) tumor bud count in cases with focally many tumor buds The "hotspot" method therefore better reflects the maximal extent of tumor budding at the invasive front.…”