Reporting of tumor budding in colorectal adenocarcinomas using ×40 objective: A practical approach for resource constrained set-ups.

Context: Tumor budding (TBud) is recognized as a poor prognostic marker in colorectal cancer (CRC) with important treatment implications in Stage II cancers and malignant polyps. There are multiple propositions for bud count reporting but without an uniformly accepted system. The International TBud consensus conference (ITBCC) proposed mandatory reporting of budding on the single worst ×20 high power field (0.785 mm area) with a 3-tier scoring system (low/intermediate/high for 0-4, 5-9, and ≥10 buds/×20 field).

Aims: Due to the lack of availability of ×20 objective, we aimed to validate a simple ×40 field count (0.236 mm area) for wider applicability.

Methods: Bud count was done on hematoxylin and eosin-stained slides of 92 archived cases of colon cancer on the worst ×20 and ×40 fields (0.95 mm and 0.236 mm area) (hotspot method). Count for 0.785 mm area was calculated using ITBCC normalization factor of 1.2. Interobserver variability between two observers was assessed. Score groups for ×20 field and proposed score groups for 40× field (low/intermediate/high for 0-1, 2-4 and ≥5 buds) were compared with disease-free survival.

Results: High bud score was seen in 20.6% and 31.5% cases, respectively, using the ×20 and ×40 methods. High interobserver concordance was noted (ICC 0.95). Both the ITBCC bud score and our proposed 40× scoring correlated significantly with prognosis (P = 0.030, log-rank test).

Conclusions: : In centers lacking 20× objective, we propose using the worst 40× hotspot method for reporting of budding for all CRCs as a simple, reproducible and prognostically significant scoring system.