CRC is the most prevalent malignancy of the gastrointestinal tract and has a high mortality rate. As reported by GLOBOCAN 2020, the number of new CRC cases worldwide is predicted to reach 3.2 million by 2040, based on aging, population growth, and human development projections1, 8, 9. In Vietnam, CRC had the fifth highest incidence rate, with 16,426 cases reported, following liver, lung, stomach, and breast cancers1.

Predicting survival outcomes in patients with colorectal adenocarcinoma remains a significant challenge, as traditional histopathological factors such as histologic type, grade, and pT stage do not always provide reliable prognostic value. In particular, histological subtypes such as signet-ring cell carcinoma and mixed adenocarcinoma are often associated with worse prognoses, making histopathology-based assessments less accurate. An increasing number of studies have confirmed that gene expression profiles and molecular characteristics offer higher prognostic value than classical histopathological factors. However, the application of molecular biology tests still faces numerous barriers, especially in developing countries such as Vietnam, due to complex technical requirements, high costs, and limited implementation in pathology laboratories. In contrast, Bd assessment using H&E-stained slides does not incur additional costs and can be easily implemented in pathology laboratories. Moreover, a standardized Bd assessment protocol based on the 2016 ITBCC recommendations has been developed, ensuring consistency and high reliability. Bd can also be evaluated consistently by different pathologists, a crucial factor that supports its use as a valuable prognostic indicator.

Bd is defined as the presence of single tumor cells or small clusters of tumor cells (< 5 cells) scattered throughout the tumor stroma. Bd is primarily assessed at the invasive tumor front; however, it has also been described within the tumor center. Lugli . reported that intratumoral budding is strongly associated with peritumoral budding and is an independent prognostic factor5. Bd is linked to the epithelial-mesenchymal transition (EMT), a process involving the loss of cell adhesion, cytoskeletal alterations, and increased extracellular matrix production5, 10.

When evaluating the relationship between Bd and histopathological tumor characteristics, we found that high-grade Bd was more prevalent in patients with deeper invasion, lymphovascular invasion, perineural invasion, and lymph node metastases (p < 0.05). Similarly, Dawson . reported that high-grade Bd was associated with tumor differentiation, invasion, lymph node metastasis, as well as lymphovascular and perineural invasion (p < 0.001)11. Shah . also identified Bd as a significant risk factor for lymph node metastasis, suggesting that it could help predict the extent of lymph node dissection. Specifically, high-grade Bd was observed in 79% of N1-stage cases and 95% of N2-stage cases12. Additionally, Brototo . demonstrated that Bd in preoperative biopsies predicts lymph node metastasis in colon carcinoma13. These findings suggest that the presence of Bd may indicate tumor invasion and spread. Therefore, assessing Bd on H&E-stained slides is essential for guiding treatment decisions and estimating patient prognosis.

A deeper analysis of OS and DFS across different Bd groups revealed that patients with high-grade Bd had significantly lower OS and DFS than those with low-grade Bd. In multivariate analysis, Bd was identified as an independent prognostic factor in CRC. High-grade Bd was also associated with higher risks of recurrence and mortality (p < 0.001), with HRs of mortality and recurrence of 45.952 and 20.652, respectively. Significant differences in OS and DFS among Bd groups were also demonstrated in both univariate and multivariate analyses (p < 0.001). Moreover, among stage II patients, high-grade Bd was associated with reduced DFS rates (57.1%, 85.7%, and 100% for high-, intermediate-, and low-grade Bd, respectively) (p = 0.001). Similarly, high-grade Bd correlated with a higher risk of recurrence, with a mean DFS time of 82.985 months for low-grade tumors, 70.8 months for intermediate-grade tumors, and 42.05 months for high-grade tumors (p < 0.001). Finally, multivariate analysis showed that high-grade Bd is an independent prognostic factor for increased recurrence risk (HR = 33.136, p < 0.01). These findings are consistent with those of previous studies. For example, Van Wyk . observed that high-grade Bd was strongly associated with disease stage, lymphovascular invasion, and decreased DFS, and was an independent prognostic indicator for patient survival irrespective of tumor stage14. Additionally, Shah observed that patients with high-grade Bd frequently experienced earlier recurrence and more extensive metastasis than other patients12. Moreover, a 2016 meta-analysis conducted by Rogers ., which included 34 studies with a total of 7,821 patients, demonstrated that Bd was a strong predictor of lymph node metastasis, recurrence, and mortality15. In addition, Betge . demonstrated that Bd was an independent predictor of disease progression (HR: 3.91, p = 0.02) and cancer-related mortality (HR: 5.9, p = 0.007)16. Lee . also found a correlation between Bd and survival (p < 0.05), suggesting that stage II CRC patient survival could be further stratified by Bd17. Finally, in a study of 200 stage II and 226 stage III CRC cases, Nakamura et al. showed that cumulative 5- and 10-year survival rates were significantly different between patients with low- and high-grade Bd (93.9% . 73.9% and 90.6% . 67.8%, respectively). Moreover, survival rates did not differ significantly between stage II patients with high-grade Bd and those with stage III disease. Cox regression analysis confirmed that Bd was an independent prognostic factor (HR = 4.89; p < 0.001)18.

Bd at the invasive front has been recognized by the Union for International Cancer Control as an unfavorable parameter and an “additional prognostic marker”19. Moreover, high-grade Bd is consistently associated with lymph node metastasis, distant metastasis, local recurrence, and the extent of invasion beyond the muscularis mucosae. Furthermore, Bd has been proposed as a useful predictor of micrometastasis in patients with node-negative CRC20 and as a key consideration for local resection in patients with T1 tumors21, 22. Multiple groups have examined the independent impact of Bd on treatment outcomes and prognosis in CRC. Some studies have shown that Bd is associated with a higher T stage5, 14, 15, 23, lymph node metastasis5, 14, 15, 23, 24, and adverse histological features independent of disease stage5, 14, 20, 23. High-grade Bd also has an independent adverse impact on both OS and DFS5, 14, 15, 16, 17, 20, 22, 23. The adverse prognostic impact of high-grade Bd is observed in both early-stage and advanced CRC and can significantly influence clinical decision-making, especially in early-stage disease. Moreover, even among patients with stage I, stage II, or node-positive disease, Bd has been shown to improve patient risk stratification16, 18, 25, 26. Taken together, Bd is considered relevant in three scenarios: (1) determining the risk of lymph node metastasis in those with early-stage CRC, thereby predicting the need for lymph node dissection; (2) identifying high-risk stage II patients requiring adjuvant therapy; and (3) its presence in the pretreatment biopsy specimen is predictive of metastasis and non-response to neoadjuvant therapy.

While molecular biomarkers such as microsatellite instability (MSI), KRAS, and BRAF mutations have demonstrated significant prognostic value in CRC, their application in routine clinical settings remains limited in many low- and middle-income countries due to high cost and lack of adequate infrastructure. In contrast, Bd can be assessed using standard H&E staining and has been widely endorsed by international guidelines for its reproducibility and prognostic relevance.

Our decision to focus on Bd rather than molecular markers was driven by both practical and clinical considerations. First, the retrospective design and resource-limited setting precluded comprehensive molecular profiling. Second, Bd offers a feasible, cost-effective, and widely applicable approach to risk stratification, especially in stage II CRC, where treatment decisions remain challenging. Third, existing literature has shown that Bd is an independent predictor of adverse outcomes, even when molecular features are accounted for. Therefore, Bd may serve as a surrogate or complementary marker to molecular assays, particularly in settings where access to advanced molecular diagnostics is restricted.

Tumor budding can be readily integrated into routine clinical practice, particularly in resource-limited environments by adhering to standardized assessment protocols. Using only H&E-stained surgical specimens, pathologists can evaluate Bd without the need for additional equipment or specialized reagents. This allows for its inclusion in routine histopathology reports, thereby enhancing the prognostic utility of these reports. Notably, Bd assessment may offer critical insights for guiding therapeutic decisions, especially in stage II CRC patients, where the indication for adjuvant chemotherapy remains a subject of clinical uncertainty.

Our findings are in line with previous studies from resource-limited settings in developing countries, which consistently demonstrate that tumor budding serves as an independent prognostic factor27, 28. These results further support its clinical utility in guiding treatment strategies. In developing countries, many cancer patients cannot afford expensive molecular tests. Since tumor budding analysis is based only on H&E-stained tissue sections, Bd may be a promising candidate for risk stratification but has received little attention in Vietnam. To our knowledge, the current study is the first in Vietnam to apply the ITBCC 2016 Bd classification to predict survival outcomes of CRC patients.

The current study has certain limitations, such as the heterogeneity of the study sample in terms of both TNM stage and treatment regimen. However, the use of the Cox proportional hazards model and multivariate regression analysis to identify factors independently associated with OS and DFS may partially reduce potential biases. Potential confounders such as comorbidities, molecular markers (., MSI status), treatment, and lifestyle factors were not controlled for. Future studies should aim to include these variables to better isolate the prognostic impact of tumor budding. Due to the retrospective and single-center design, selection bias cannot be excluded. Future prospective multicenter validation studies with larger sample sizes are necessary to confirm our findings.