Tumor budding (TB) in Colorectal Cancer (CRC), The Best Slide To Count On!

Abstract

Abstract Introduction/Objective TB is a strong prognosticator in CRC. The international TB consensus conference (ITBCC, 2016) proposed a “hot spot” approach for TB grading. We aimed to identify the characteristics of sections with the highest TB grade utilizing ITBCC’s method. Methods Resected CRC cases, excluding treated cases, were retrieved. All tumor sections were examined. Section TB grade(sTB) was noted. The highest sTB was deemed the final TB grade(fTB) of each case. The following categories were assessed: 1) maximum T stage; 2) presence of benign mucosa; 3) presence of a precursor lesion; 4) highest tumor volume; 5) presence of lymphovascular invasion(LVI). In cases where a given category was demonstrated in >1 section, the section with the highest sTB was used. High risk features (HFR) included T4, <12 lymph nodes, positive margin, high grade tumor, perineural invasion and LVI. Pearson’s correlation was performed to compare two groups using a p-value of <0.05. Results 147 cases were examined. fTB was 1=25.2%, 2=40.8% and 3=34%. 63 tumors involved the left colon and 62 had nodal disease. Of 119 cases with known MMR status 44 were MMR deficient. sTB was uniform across the categories in 101(68.7%) and uneven in 46(32.3%) cases. 12(24.5%) of 49 stage II CRC without HRF showed uneven sTB, with 2 showing 2-tier discrepancy (sTB1, fTB3). sTB was highest for category 3 (94.1%, P<.001), followed by category 2 (91.8%, P<.001), and lowest for category 1 (82.3%, P<.001), which remained true after subgrouping by MMR status and tumor location. Conclusion While about 70% of cases showed uniform TB grading across categories, choosing the slide(s) with a precursor lesion or benign mucosa increases the probability of correctly grading TB. Given the management implication, it may be prudent to scan all tumor slides in stage II CRC without HRF to avoid under-grading of TB.