Oral squamous cell carcinoma (OSCC) is one of the most common malignancies affecting the head and neck region and represents a major public health problem, particularly in developing countries like India. OSCC accounts for over 90% of all oral cancers and is characterized by a high propensity for local invasion and regional lymph node metastasis, contributing to poor survival outcomes despite advances in diagnostic and therapeutic strategies (Warnakulasuriya, 2009)[1].

India bears a disproportionately high burden of oral cancers globally, with over 135,000 new cases diagnosed annually, many of which are linked to tobacco use in the form of smoking, chewing betel quid, and gutkha [2](Gupta et al., 2013). In the state of Tamil Nadu, the prevalence is significantly elevated, especially among low-income, rural populations where risk habits are widespread and access to early screening is limited[3] (Elango et al., 2011). The five-year survival rate for OSCC remains stagnant at around 50–60%, primarily due to late-stage diagnosis and lack of effective prognostic markers for risk stratification (Sankaranarayanan et al., 2013)[4].

In recent years, tumour budding — defined as the presence of single cells or small clusters of fewer than five tumour cells at the invasive tumour front — has emerged as a promising histopathological indicator of tumour aggressiveness. Tumour budding reflects the epithelial–mesenchymal transition (EMT), a process that facilitates invasion and metastasis (Zlobec & Lugli, 2010)[5]. Several studies have established the prognostic value of tumour budding in colorectal, pancreatic, and esophageal carcinomas. More recently, its role in OSCC has gained attention. For instance, Almangush et al.[6] (2015) and Boxberg et al.[7] (2019) demonstrated a significant association between high tumour budding activity and poor overall survival, increased lymph node metastasis, and advanced stage in OSCC patients.

Despite this growing evidence, tumour budding has not yet been incorporated into routine histopathological reporting of OSCC, particularly in Indian clinical practice. There is a scarcity of region-specific data, especially from South Indian populations such as those in Tamil Nadu, where genetic, environmental, and lifestyle-related factors may influence tumour behavior. Given the simplicity and cost-effectiveness of tumour budding evaluation on conventional hematoxylin and eosin (H&E) stained sections, its incorporation could serve as a valuable tool for prognostication in resource-constrained settings.

Justification of the Study

This study is undertaken to bridge the gap in regional data regarding tumour budding in OSCC and to evaluate its correlation with established clinicopathological parameters and survival outcomes. By validating tumour budding as a prognostic marker in a South Indian population, particularly in Tamil Nadu, this research aims to support its inclusion in routine histopathological assessment and contribute to individualized patient management.

AIM AND OBJECTIVES

To assess the prognostic significance of tumour budding at the invasive front in patients with oral squamous cell carcinoma (OSCC) in a tertiary care centre in Tamil Nadu.

Objectives:

1. To evaluate the association between tumour budding and clinicopathological parameters such as tumour grade, stage, lymph node involvement, and depth of invasion in OSCC.
2. To determine the correlation between high-grade tumour budding and overall survival or disease-free survival in OSCC patients.

Study Design and Setting

This was a retrospective observational study conducted in the Department of Pathology at a tertiary care hospital in Tamil Nadu. The study period spanned five years, from January 2018 to December 2023. The study aimed to evaluate the prognostic significance of tumour budding at the invasive front in patients diagnosed with oral squamous cell carcinoma (OSCC).

Study Population

The study included 120 histopathologically confirmed cases of OSCC obtained from archival formalin-fixed, paraffin-embedded (FFPE) tissue blocks. These cases were selected from patients who had undergone biopsy or surgical resection at the institution during the study period.

Inclusion Criteria

• Patients with histologically confirmed OSCC.
• Availability of adequate tissue sections showing the invasive front.
• Complete clinical and pathological data including TNM staging and follow-up information (minimum 24 months post-diagnosis).

Exclusion Criteria

• Cases with recurrent OSCC or previously treated with chemotherapy/radiotherapy.
• Inadequate tissue sections for tumour budding assessment.
• Poorly preserved or autolyzed specimens.
• Patients lost to follow-up before 24 months.

Data Collection

Demographic and clinical data including age, sex, tumour site, history of tobacco use, and clinical stage were retrieved from patient records. Histopathological details including tumour grade, depth of invasion (DOI), lymphovascular invasion, perineural invasion, and lymph node status were noted from pathology reports.

Histopathological Assessment of Tumour Budding

Hematoxylin and eosin (H&E) stained sections from representative blocks were reviewed under light microscopy by two independent pathologists, blinded to the clinical outcomes.

Tumour budding was defined as the presence of isolated single cancer cells or small clusters comprising fewer than five cells at the invasive front of the tumour. The area with the highest budding activity (hotspot) was identified under low power, and the number of tumour buds was counted in a field measuring 0.785 mm² at 20x magnification, as per recommendations by the International Tumor Budding Consensus Conference (ITBCC).

Cases were categorized into:

• Low-grade budding: ≤4 buds
• High-grade budding: ≥5 buds

Follow-Up and Outcome Assessment

Clinical follow-up data were obtained from patient records and hospital registries for a minimum of 24 months. The primary outcome measures were:

• Disease-free survival (DFS): Defined as the time from diagnosis to recurrence.
• Overall survival (OS): Defined as the time from diagnosis to death due to disease.

Statistical Analysis

Data were entered into Microsoft Excel and analyzed using SPSS version 26.0 (IBM Corp., Armonk, NY, USA). Categorical variables were summarized as frequencies and percentages. Associations between tumour budding and clinicopathological variables were assessed using the Chi-square test or Fisher’s exact test, as appropriate. Survival outcomes were analyzed using the Kaplan-Meier method, and differences were assessed with the log-rank test. A p-value < 0.05 was considered statistically significant.

Table 1: Baseline Demographic and Clinical Profile of OSCC Patients (n = 120)

The study included 120 patients who underwent resection for OSCC. The commonest affected age group was 51-60years (35%) followed by >60yrs age group (26.7%).

Majority of the patients were male (72.5%) and about 102 individuals(85%) had a habit of tobacco or bettel nut chewing. Buccal mucosa was the commonest affected site with 58 (48.5%) cases followed by tongue with 35 cases (29.2%).

Table 2: Association of Tumour Budding with Histopathological Parameters

Table 3: Association between Tumour Budding and Lymph Node Metastasis

Table 4: Correlation between Tumour Budding and TNM Stage

Predominant of the well differentiated tumors had a low tumor budding when compared to the moderately and poorly differentiated tumors with high tumor budding. Also the majority of the tumors with greater DOI (>4mm) , LVI and a positive nodal status showed  higher tumor budding. These findings had high statistical significance with p<0.001. The tumor budding association with the Tumor stage also showed high statistical significance with a p<0.01, with the stage 3,4 tumors showing high tumor budding.

Table 5: Survival Outcome Based on Tumour Budding (2-Year Follow-Up)

Over 52 (86.7%)  cases of the 60 tumors with low tumor budding had a 2 year Disease free survival , when compared to the DFS rate (41.7%) of tumors with high tumor budding. The 2-year recurrence rate and death rate of tumors with high tumor budding was higher, 33.3% and 25% respectively.  

The present retrospective analysis was conducted to evaluate the significance of tumour budding at the invasive front in oral squamous cell carcinoma (OSCC) and its association with various clinicopathological features and survival outcomes. Our findings reaffirm the growing evidence that tumour budding is a powerful, independent prognostic marker in OSCC.

In our study, high-grade tumour budding (≥5 buds per 0.785 mm²) was observed in 42.5% of the cases. This finding is consistent with the study by Almangush et al.[6] (2015), who reported a similar prevalence of high tumour budding in OSCC and demonstrated its strong correlation with reduced survival and lymph node metastasis. Similarly, Boxberg et al.[7] (2019) found that higher tumour budding activity was associated with worse outcomes and proposed an adjusted grading system that incorporated tumour budding and cell nest size.

A significant association was observed between high tumour budding and poor histological differentiation in our cohort (p < 0.01). This aligns with the observations by Yue et al.[8] (2020), who found that poorly differentiated OSCC cases had significantly more budding foci, suggesting that tumour budding may be a histological representation of epithelial–mesenchymal transition (EMT).

We also found that high tumour budding was significantly associated with deeper invasion (DOI >10 mm), higher TNM stage, and the presence of lymphovascular invasion (LVI) and perineural invasion (PNI). These findings are comparable to those reported by Alka et al.[9] (2019) in a study on Brazilian OSCC patients, where high tumour budding was linked to DOI >4 mm, advanced tumour stage, and LVI/PNI, reinforcing the role of tumour budding in indicating aggressive tumour biology.

With respect to nodal metastasis, our study showed that 66.7% of patients with high tumour budding had cervical lymph node involvement (p < 0.001). This is in concordance with a multicenter study by Shota et al.[10] (2018), who showed that tumour budding was significantly associated with nodal positivity and proposed its utility in predicting occult metastasis, especially in early-stage tumours.

Regarding prognostic outcomes, the Kaplan–Meier survival analysis in our study demonstrated that patients with high tumour budding had significantly lower overall survival (OS) and disease-free survival (DFS) compared to those with low tumour budding (p < 0.01). These findings mirror those of Wang et al.[11] (2011), who reported that tumour budding was a reliable histopathological indicator for predicting recurrence and poor survival in OSCC patients.

An important strength of our study is its focus on a South Indian population, where lifestyle habits such as smokeless tobacco use, betel quid chewing, and poor oral hygiene contribute to distinct tumour biology. While international studies have established tumour budding as a prognostic factor, regional validation such as this study is essential for its integration into histopathological protocols in Indian clinical settings.

However, this study is not without limitations. Being retrospective in design, it is limited by the quality of archived data and follow-up records. Interobserver variability, though minimized by blinding, may influence tumour budding counts. Additionally, immunohistochemical markers (e.g., pancytokeratin) were not employed, which could further improve the detection of isolated tumour cells, especially in stromal-rich areas.

Despite these limitations, our study supports the growing consensus that tumour budding is a robust, reproducible, and cost-effective histopathological marker of poor prognosis in OSCC. Incorporating tumour budding into routine histopathology reporting may enhance risk stratification, guide clinical decision-making, and identify patients who might benefit from more aggressive treatment.

This retrospective analysis highlights that tumour budding at the invasive front is a significant histopathological marker associated with aggressive behavior in oral squamous cell carcinoma. High-grade tumour budding demonstrated strong correlations with adverse prognostic features such as poor tumour differentiation, deeper invasion, lymphovascular invasion, higher TNM stage, and increased lymph node metastasis. Furthermore, patients with high-grade tumour budding had significantly lower disease-free and overall survival rates. Given its simplicity, reproducibility, and prognostic relevance, tumour budding should be routinely evaluated in histopathological reporting of OSCC, especially in resource-limited settings like those in Tamil Nadu, to guide risk stratification and inform therapeutic decisions

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