Immunolocalization of Cancer Stem Cells Marker ALDH1 and its Association with Tumor Budding in Oral Squamous Cell Carcinoma

Study on Tumor Budding and Immunoexpression of Cancer Stem Cell Marker ALDH1 in Oral Squamous Cell Carcinoma

Background Tumor budding refers to the presence of individual cancer cells or small clusters of cells that break away from the main tumor and are seen at the edge where the tumor is invading surrounding tissue. Aldehyde dehydrogenase 1 is a cancer stem cell marker that causes oxidation of retinol to retinoic acid in early stem cell differentiation. This study aimed to examine tumor budding in oral squamous cell carcinoma and explore how it relates to various clinical and pathological factors. A study of cancer stem cell marker ALDH1 was also done with correlation to tumor budding and prognostic markers. Material and methods A prospective study was carried out in a pathology department over one year and included all newly diagnosed cases of oral squamous cell carcinoma that had undergone surgical resection. Both the gross specimens and the tissue sections stained with hematoxylin and eosin (H&E) from paraffin-embedded samples were examined for tumor size, histopathological grade, in situ carcinoma, necrosis, lymphovascular emboli, perineurial invasion, and lymph node metastasis. Tumor budding was evaluated for every case by observing tumor buds (clusters of a single tumor cell or a small cluster of tumor cells (<5) at the invasive front of the tumor) at 40x. Immunohistochemical analysis for ALDH-1 was performed on paraffin-embedded histopathological sections. Results A total of 50 cases were included in the study, with a mean age of 49 years and a male-to-female ratio of 7.3:1. The most common site of carcinoma was buccal mucosa (34%), followed by tongue (30%). Ninety percent (90%) of cases were moderately differentiated squamous cell carcinoma, with 82% of cases showing lymphovascular emboli and 32% showing perineural invasion. The highest number of cases, 22% (11), were classified as pT4aN0Mx, followed by 16% (8 cases each) classified as pT2N0Mx and pT3N0Mx. Sixty-six percent (66%; n=33) of cases showed high-grade tumor budding while 34% (n=17) showed low-grade tumor budding. Eighty-eight point eight percent (88.8%; n=32) of cases with high-grade tumor budding as well as lymphovascular invasion were observed with a statistically significant association (p=0.042). The study found a statistically significant link between high-grade tumor budding and the presence of lymph node metastasis (p=0.003). Fifty-eight percent (58%) of cases showed positive immunostaining of ALDH1 with varying intensity from weak to strongly positive. ALDH1 expression showed a significant association with high-grade tumor budding, with the result being statistically highly significant (p = 0.0001). Conclusion High-grade tumor budding is associated with increased expression of cancer stem cell marker ALDH1 in oral squamous cell carcinoma. It is also associated with lymphovascular invasion and lymph node metastasis, suggesting a poor prognosis in these patients. It is recommended that tumor budding should be included in histopathological reports of oral carcinoma. ALDH1 may be explored as a potential target for therapy in oral carcinoma. The authors suggest that further larger studies with extended follow-up may be done to establish the role of tumor budding and ALDH1 in the prognosis of oral carcinoma.

ALDH1 Immunohistochemical expression and its association with tumor budding in oral squamous cell carcinoma of gingivobuccal complex

Background:

Aldehyde dehydrogenase 1 is a potential biomarker for cancer stem cells (CSCs), pertinent to tumorigenesis and treatment resistance, whereas tumor buds (TB) are small nests of tumor cells scattered in the stroma of tumor front. This study evaluated the interrelationship of TBs with CSCs in oral squamous cell carcinoma (OSCC) cases of gingivobuccal complex.

Methods:

An immunohistochemical study was conducted on paraffin-embedded sections of 50 cases of OSCC of gingivobuccal complex with Pan-CK for TB and ALDH1 for CSCs. Correlations were assessed between the semiquantitative scoring for immunohistochemical expression of ALDH1 and tumor budding intensity. Statistical evaluation was performed by the Chi-square test, and cutoff score was determined by employing ROC curve.

Results:

A significant correlation of ALDH1 expression was attained between the groups both inside (P = 0.031) and outside (P = 0.028) the budding area, reflecting a spatial distribution of CSCs in the tumor front. The ROC curve analysis suggested a cutoff value of 11%-50% ALDH1 expression inside TB area, demonstrating 76% of sensitivity and specificity of 63%, which may better predict aggressive behavior and poorer prognosis than TB alone in OSCC.

Conclusion:

ALDH1 expression inside and outside the budding area correlated significantly with TB intensity, suggesting that TBs have CSCs-like phenotype predisposing to migratory and invasive properties.

Tumor budding is a prognostic marker for overall survival and not for lymph node metastasis in Oral Squamous Cell Carcinoma - Systematic Review Update and Meta-Analysis

Objective

Tumor budding (TB) has shown promising results as a prognostic marker in several cancers such as colorectal carcinoma, breast carcinoma etc. It has been co-related to aggressiveness of the tumor and can also predict the metastasis to the lymph nodes. This systematic review evaluates the prognostic potential of TB in predicting lymph node metastasis (LNM) in OSCC.

Data sources

Systematic search was carried out in the electronic data-bases i.e. PubMed, Cochrane and Google scholar for original studies related to TB in OSCC. The assessment of risk bias was done using QUIPS tool. Meta-analysis was done using STATA software.

Results

A total of 25 articles were included. A significant association was noted for overall survival and prognosis but not for TB LNM in OSCC. Meta-analysis revealed a pooled estimate i.e odds ratio of 2.10 (CI - 0.00 - 4.20) for TB and LNM while for overall survival, it was 2.29 (CI-1.81-2.76).

Conclusion

Tumor budding though is strongly associated with LNM in OSCC did not show significant relationship in this systematic review but demonstrated a higher correlation with overall survival. It highlights that TB is an important parameter for prognosis of oral cancer but its potential in prediction of LNM needs further validation.

ALDH1 immunoexpression in epithelial and stromal cells of oral lichen planus and lesions with lichenoid inflammatory infiltrate

BACKGROUND

Oral Lichen Planus is a potential malignant disorder and shares clinical and histopathological features with other similar lesions. ALDH1 is a specific biomarker for stem cells identification, however its role in stromal cells of immune inflammatory infiltrate has not been explored. The aim of this study was to investigate the ALDH1 immunoexpression in epithelial and stromal cells of Oral Lichen Planus and other lesions with lichenoid inflammatory infiltrate.

MATERIAL AND METHODS

64 samples of Oral Lichen Planus, Oral Lichenoid Lesions, Oral Leukoplakia and Unspecific Chronic Inflammation were included. ALDH1 was evaluated in both epithelium and stromal cells. ALDH1+ cells ≥ 5% were considered positive in epithelium. Stromal cells were evaluated semi quantitatively. Fields were ranked in scores, according to criteria: 1 (0 to 10%); 2 (11 to 50%) and 3 (>50%). The mean value of the sum of the fields was the final score. Statistical differences among groups were investigated, considering p < 0.05.

RESULTS

ALDH1 expression in epithelium was low in all groups without difference among them. ALDH1+ cells in the lamina propria were higher for Lichen Planus [2.0], followed by Leukoplakia [1.3], Lichenoid lesions [1.2] and control [1.1] (p<0.05).

CONCLUSIONS

ALDH1 immunoexpression in epithelium of lichenoid potential malignant disorders did not show a contributory tool, however ALDH1 in stromal cells of lichen planus might be involved in the complex process of immune regulation associated with the pathogenesis of this disease.

Mitochondria in oral cancer stem cells: Unraveling the potential drug targets for new and old drugs

Head and neck cancer is a major health problem worldwide, with most cases arising in the oral cavity. Oral squamous cell carcinoma (OSCC) is the most common type of oral cancer, accounting for over 90% of all cases. Compared to other types of cancer, OSCC, has the worse prognosis, with a 5-year survival rate of 50%. Additionally, OSCC is characterized by a high rate of resistance to chemotherapy treatment, which may be partly explained by the presence of cancer stem cells (CSC) subpopulation. CSC can adapt to harmful environmental condition and are highly resistant to both chemotherapy and radiotherapy treatments, thus contributing to tumor relapse. The aim of this review is to highlight the role of mitochondria in oral CSC as a potential target for oral cancer treatment. For this purpose, we reviewed some fundamental aspects of the most validated protein markers of stemness, autophagy, the mitochondrial function and energy metabolism in oral CSC. Moreover, a discussion will be made on why energy metabolism, especially oxidative phosphorylation in CSC, may offer such a diverse source of original pharmacological target for new drugs. Finally, we will describe some drugs able to disturb mitochondrial function, with emphasis on those aimed to interrupt the electron transport chain function, as novel therapeutic strategies in multidrug-resistant oral CSC. The reutilization of old drugs approved for clinical use as new antineoplastics, in cancer treatment, is also matter of revision.

Predictive value of tumor budding in head and neck squamous cell carcinoma: an update

Head and neck squamous cell carcinoma forms an anatomically and functionally complex group of malignancies. The significant local aggressiveness and frequent regional relapses motivate ongoing research to identify more reliable and sensitive prognostic and predictive biomarkers. One emerging area of cancer biology is the evaluation of tumor budding at the advancing invasive front of various types of epithelial cancers. Recent studies suggest that tumor budding is a relatively common phenomenon in cancer progression and that it may have important prognostic implications for patients due to its potential to provide valuable insights into the biology and clinical behavior of head and neck cancer. In this review, we aim to provide information about tumor budding in head and neck squamous cell carcinoma. Thus, we hope to shed light on the complex biology of these malignancies, as well as aiding diagnostic, classification, and better characterization and thereby, looking for new avenues for improving patient outcomes.

Microvascular density and tumor budding in oral squamous cell carcinoma

BACKGROUND

Oral squamous cell carcinoma (OSCC) is the most prevalent malignant head and neck tumor, excluding the nonmelanoma skin cancer. Despite recent advances in the diagnosis and treatment, the disease's mortality rate is nonetheless high. The presence of isolated neoplastic cells or small clusters of up to four cells at the tumor's invasive front, named tumor budding, is associated with a worse prognosis in OSCC. Angiogenesis has also been recognized as a determining factor in the progression of malignancies and in the development of metastases. Several studies have investigated the assessment of microvascular density (MVD) as a potential prognostic factor in OSCC. This study aimed to evaluate, in OSCC, differences in MVD between tumors with high-intensity tumor budding and tumors with low-intensity or no tumor budding. In samples with high-intensity tumor budding, differences in MVD between the budding area and the area outside the budding were also evaluated. Moreover, the study assessed differences in MVD concerning clinicopathological characteristics such as sex, age, tobacco smoking, tumor location and tumor size.

MATERIAL AND METHODS

One hundred and fifty [150] samples of OSCC were subjected to immunohistochemistry to assess the intensity of tumor budding (by immunostaining for multi-cytokeratin) and MVD (by immunostaining for CD34 and CD105, independently). The data were treated using descriptive and analytical statistics.

RESULTS

There were no differences in MVD, assessed by immunostaining for CD34 or CD105, concerning clinicopathological characteristics such as sex, age, tobacco smoking, tumor location and tumor size (p > 0.05). Tumors with high-intensity tumor budding did not show differences in MVD, assessed by immunostaining for CD34 or CD105, when compared to tumors with low-intensity or no tumor budding (p > 0.05). However, in samples with high-intensity tumor budding, the MVD assessed by immunostaining for CD34 was higher in the budding area than in the area outside the budding (p < 0.05). This difference was not observed when MVD was assessed by immunostaining for CD105 (p > 0.05).

CONCLUSIONS

The higher MVD in the budding area may be an additional indication that this is a peculiar region of the tumor, associated with biological phenomena related to tumor progression.

Relationship between Tumor Budding and Partial Epithelial-Mesenchymal Transition in Head and Neck Cancer

Tumor budding (TB), a microscopic finding in the stroma ahead of the invasive fronts of tumors, has been well investigated and reported as a prognostic marker in head and neck squamous cell carcinoma (HNSCC). Epithelial-mesenchymal transition (EMT) is a crucial step in tumor progression and metastasis, and its status cannot be distinguished from TB. The current understanding of partial EMT (p-EMT), the so-called halfway step of EMT, focuses on the tumor microenvironment (TME). Although this evidence has been investigated, the clinicopathological and biological relationship between TB and p-EMT remains debatable. At the invasion front, previous research suggested that cancer-associated fibroblasts (CAFs) are important for tumor progression, metastasis, p-EMT, and TB formation in the TME. Although there is biological evidence of TB drivers, no report has focused on their organized functional relationships. Understanding the mechanism of TB onset and the relationship between p-EMTs may facilitate the development of novel diagnostic and prognostic methods, and targeted therapies for the prevention of metastasis in epithelial cancer. Thus far, major pieces of evidence have been established from colorectal cancer (CRC), due to a large number of patients with the disease. Herein, we review the current understanding of p-EMT and TME dynamics and discuss the relationship between TB development and p-EMT, focusing on CAFs, hypoxia, tumor-associated macrophages, laminin-integrin crosstalk, membrane stiffness, enzymes, and viral infections in cancers, and clarify the gap of evidence between HNSCC and CRC.

The Emerging Impact of Tumor Budding in Oral Squamous Cell Carcinoma: Main Issues and Clinical Relevance of a New Prognostic Marker

Tumor Budding (TB) represents a single cancer cell or a small cluster of less than five cancer cells on the infiltrative tumor front. Accumulating evidence suggests TB is an independent prognostic factor in oral squamous cell carcinoma (OSCC). However, its exact role is not yet elucidated, and a standardized scoring system is still necessary. The study aims to extensively review the literature data regarding the prognostic role of TB in OSCC. The results of TB are an independent prognostic factor of poor survival outcomes in OSCC. To date, the manual detection of hematoxylin and eosin-staining or pancytokeratin-immunostaining sections are the most commonly used methods. Between the several cut-offs, the two-tier system with five buds/field cut-offs provides better risk stratification. The prognostic role of the BD model in predicting survival outcomes was extensively validated; however, the inclusion of DOI, which is already a staging parameter, encouraged other authors to propose other models, integrating TB count with other adverse risk factors, such as the tumor–stroma ratio and tumor-infiltrated lymphocytes. The prognostic relevance of TB in OSCC highlights its evaluation in daily pathological practice. Therefore, the TB detection method and the TB scoring system should be validated based on tumor stage and site.

Tumor budding of cervical squamous cell carcinoma: epithelial-mesenchymal transition-like cancer stem cells?

Recent evidence indicates that cancer stem cells (CSCs) are the origin of cancers. Scientists have identified CSCs in various tumors and have suggested the existence of a variety of states of CSCs. The existence of epithelial-mesenchymal transition (EMT)-like CSCs has been confirmed in vitro, but they have not been identified in vivo. Tumor budding was defined as single cell or clusters of ≤ 5 cells at the invasive front of cancers. Such tumor budding is hypothesized to be closely related to EMT and linked to CSCs, especially to those migrating at the invasive front. Therefore, tumor budding has been proposed to represent EMT-like stem cells. However, this hypothesis has not yet been proven. Thus, we studied the expression of EMT markers, certain CSC markers of tumor budding, and the tumor center of cervical squamous cell carcinoma (CxSCC). We performed tissue chip analyses of 95 primary CxSCCs from patients. Expression of EMT and CSC markers (E-cadherin, β-catenin, vimentin, Ki67, CD44, SOX2 , and ALDH1A1) in a set of tumor samples on tissue chips (87 cases of tumor budding/the main tumor body) were evaluated by immunohistochemistry. We found that the cell-membranous expression of β-catenin was stronger in the main tumor body than in tumor buds. Compared with the main tumor body, tumor buds had reduced proliferative activity as measured by Ki67. Moreover, vimentin expression was high and E-cadherin expression was low in tumor buds. Expression of EMT-related markers suggested that tumor buds were correlated with EMT. We noted that CxSCC tumor buds had a CD44negative/low/SOX2high/ALDH1A1high staining pattern, indicating that tumor buds of CxSCC present CSC-like immunophenotypic features. Taken together, our data indicate that tumor buds in CxSCC may represent EMT-like CSCs in vivo.

[Cancer stem cells in oral squamous cell carcinoma. Literature review]

Objective

To perform a literature review on oral squamous cell carcinoma, the presence of cancer stem cells; their association with the course of the disease and therapeutic applications.

Methods

: A search was performed in the PubMed database by entering the following algorithm: ((((neoplastic stem cells [MeSH Terms ]) OR (Cancer stem cells [Text Word ])) AND (Squamous Cell Carcinoma of Head and Neck [MeSH Terms])) AND (Oral squamous cell carcinoma [Text Word ]), to find articles in english published between 2012 and 2022. The PRISMA diagram was used to identify and select the articles.

Results

A result of 49 articles was obtained; of which 27 were chosen according to the title and abstract in their association with the topic. In addition, 8 additional articles suggested by their relationship with the information previously searched were included. In total, 35 articles were evaluated. There has been found that tumoral cells in squamous oral carcinoma are heterogeneous since they include cancer stem cells wich possess characteristics of stem and neoplasic cells; which possess characteristics of stem cells as well as neoplastic cells; they have been associated with disease progression, recurrence, and metastasis and have been considered to be a key mechanism of therapy failure.

Conclusions

The expression of stem cell markers in oral squamous cell carcinomas has been demonstrated and has contributed to their identification in oral squamous cell carcinomas and has been implicated in the behavior of cancer cells. New therapeutic measures aimed at eliminating cancer stem cells have been proposed and developed.

Prognostic significance of tumor budding thresholds in oral tongue squamous cell carcinoma

Oral tongue squamous cell carcinoma (OTSCC) represents the most common malignancy of the oral cavity. Tumor budding (TB) is a reliable prognostic factor in OTSCC; however, a standardized scoring system is not still validated. The study aims to evaluate the prognostic role of TB in 211 OTSCC patients treated between 1997-2018. TB was evaluated on haematoxylin and eosin-stained sections in the hotspot area of the infiltrative front (×200-magnification). It was scored using a two-tier, a three-tier system, and according to BD-model and revised-Grading system. Univariate and multivariate Cox regression analyses of disease-specific survival (DSS) and disease-free survival (DFS) were performed. A p-values<0.05 was considered as statistically significant. The two-tier and three-tier system resulted an independent prognostic factor of DSS. High-risk patients had a 2.21 and 3.08 times-increased probability of poor DSS compared to low-risk group. It is significantly increased even for intermediate-risk group. No significant differences emerged classifying patients according to BD-model and revised-Grading. These data confirm the prognostic value of TB in predicting DSS in OTSCC. Classifying patients in two groups using the 5-buds cut-off significantly discriminates their outcomes. Since the established role of DOI and the poor prognostic value of grading, TB could be considered an independent prognostic marker.

Expression of aldehyde dehydrogenase 1A1 in oral squamous cell carcinoma and its correlation with clinicopathological parameters

Background:

Materials and Methods:

Results:

Conclusion:

Clinicopathological correlation of stem cell markers expression in oral squamous cell carcinoma; relation to patients` outcome

Background: Squamous cell carcinoma (OSCC) is the commonest oral malignancy.The overall 5 year survival of OSCC has remained at 50%, largely unchanged for 40 years. CSCs are important within the development, invasion, drug resistance, and prediction of carcinomas treatment outcome. ALDH1 and CD44 are commonly used epithelial tumors cancer stem-like cells surface markers. Materials: Our study aimed to judge CD44 and ALDH1 immunohistochemical expressions in 44 cases of OSCC and relates the expression to patients' survival. Results: High CD44 & ALDH1 expressions were significantly expressed in variable histologic grades of OSCCs, large sized carcinomas, presence lymph vascular invasion, presence of nodal and distant metastasis, advanced TNM clinical stage, recurrence and death during follow up period (P ≤ 0.05). Reduced DFS and three years overall survival were significantly recorded in cases with high CD44 expression, and high ALDH1 expression (p < 0.05). CD44 & ALDH1 expressions, histologic grade, tumor size were the independent predictors of DFS and three years OS. Conclusion: CD44 and ALDH1 expressions are valuable prognostic factors in OSCC and could be well considered predictors for patients' 3 years OS and DFS.

Overexpression of ALDH1 and EMT marker profile are linked with unfavorable outcome in head and neck cancer

Background

The aim of this research was to assess the expression of aldehyde dehydrogenase 1 (ALDH1) and epithelial-mesenchymal transition (EMT) markers in head and neck squamous cell carcinoma (HNSCC), and to correlate them with the clinical and histopathological parameters of a patient cohort with follow-up over an 8-year period.

Material and Methods

For this, seventeen HNSCC and non-neoplastic adjacent epithelium (AE) samples were subjected to laser microdissection and real-time PCR to evaluate the mRNA expression of ALDH1, E-cadherin (E-CAD), N-cadherin (N-CAD), and vimentin (VIM). Also, immunohistochemistry was performed for ALDH1, E-CAD, N-CAD, and VIM in the tumor center (TC), invasion front (IF), and AE of the seventeen samples. Mann-Whitney, Kruskal-Wallis and Chi-square tests were used to correlate the mRNA and immunohistochemical expression with different variables, considering p<0.05. Kaplan-Meier curves were produced for local recurrence, regional metastasis and treatment.

Results

A mRNA overexpression of ALDH1 in primary tumors was associated with regional metastasis and a high ALDH1 immunostaining was related to metastasis and a worse patient outcome. Additionally, a favorable outcome was associated with the transition phase and an unfavorable outcome was associated with EMT event. An overall 26.9 months was observed with longer survival associated with surgery and radiotherapy.

Conclusions

However, due to the intense variability inherent to the indicator proteins in the EMT process, the complete profile markers related to this biological process should be continuous investigated.

Key words:Aldehyde dehydrogenase 1, epithelial mesenchymal transition, head and neck cancer, squamous cell carcinoma, follow-up study.

Tumour budding in solid cancers

Tumour budding is an emerging prognostic biomarker in colorectal cancer (CRC) and other solid cancers. Tumour buds are usually defined as isolated single cancer cells or clusters of up to four cancer cells located at the invasive tumour front. The prognostic value of tumour budding is now supported by a large body of evidence, whereas the utility of this phenotype as a predictive biomarker remains under investigation. The application of tumour budding indices in clinical practice requires a standardized scoring system that can be tailored to specific tumour types and clinical scenarios. In the context of CRC, tumour budding can be assessed according to the method agreed at the International Tumour Budding Consensus Conference (ITBCC) in 2016. Using the ITBCC scoring system, tumour budding is an independent predictor of lymph node metastasis in patients with pT1 CRC and of unfavourable survival in patients with stage II colon cancer. Regardless of the clinical scenario or tumour type, the assertion that 'the more tumour buds, the worse the clinical outcome' applies. In this Review, we provide an overview of tumour budding in solid cancers, highlighting the molecular and biological aspects of this phenomenon, including its associations with epithelial-mesenchymal transition and features of the tumour microenvironment. We also describe the available evidence demonstrating the value of tumour budding as a biomarker across various solid cancers.

Salicylate sensitizes oral squamous cell carcinoma to chemotherapy through targeting mTOR pathway

Oral squamous cell carcinoma (OSCC) is an extremely aggressive neoplasm, which is usually diagnosed in the advanced stage of the disease. Extensive studies have shown a link between chronic inflammation and various types of cancer, including OSCC. Salicylate is a biotransformation product of aspirin, with similar anti-inflammatory ability to aspirin but lacks aspirin's inhibitory effect on the isolated cyclooxygenase activity. Our study indicates that salicylate sensitizes OSCC to anti-cancer drugs, but the mechanisms of its action are unclear. Here, OSCC cells were used to evaluate the cytotoxicity of salicylate alone or in combination with cisplatin (CDDP). RPPA proteomic array and Western blotting were employed to determine the signaling pathways affected by salicylate. Salicylate decreased cell survival rate and induced cell apoptosis in OSCC cells but not human normal oral mucosal epithelial cells (hTERT-OME). The use of sodium salicylate (SS) dramatically sensitized OSCC cells to CDDP. RPPA array showed that SS reduced many oncogenes such as PI3K/mTOR signaling and cancer stem cell (CSC)-related genes versus control. Western and transcriptional analyses substantiated that salicylate down-regulated these CSC-associated genes and the mTOR pathway dose dependently. Salicylate preferentially repressed the ability of sorted ALDH1+ cells to form tumor spheres. Finally, salicylate suppressed tumor growth in vivo, and the combination of salicylate and CDDP further synergistically reduced the growth of tumors. Salicylate hinders OSCC cell growth and sensitizes OSCC cells to CDDP through targeting CSCs and the mTOR signaling pathway. We propose that salicylate is beneficial for OSCC patients, and salicylate may be combined with chemotherapies to effectively treat OSCC patients.

Tumor budding is a potential histopathological marker in the prognosis of oral squamous cell carcinoma: Current status and future prospects

Tumor budding (TB) is a histopathologically evident feature that represents a scattered pattern of invasion consisting of isolated single tumor epithelial cells or tumor cells in small clusters (up to 5 cells) seen primarily at the invasive front dispersed within the stroma for variable distance. Presence of TB has been linked with lymph node metastasis, recurrence, distant metastasis and reduced survival in numerous cancers including oral squamous cell carcinoma (OSCC). Tumor buds are also considered as histopathological markers of epithelial-mesenchymal transition which is a molecular process implicated as a hallmark for invasion and metastasis. This review gives an overview of the current evidence regarding TB assessment in OSCC and its future prospects.

Hallmarks of cancer: Tumor budding as a sign of invasion and metastasis in head and neck cancer

Invasion and metastasis are hallmarks of cancer. The concept of tumor budding at tumor-host interface has been documented in many carcinomas. A growing body of evidence indicates that tumor budding is a sign of invasion and early step for metastasis of many epithelial cancers including head and neck squamous cell carcinoma (HNSCC). In addition, recent research has underlined the importance of tumor budding as a promising prognosticator in HNSCC. This review summarizes the findings regarding tumor budding in HNSCC and focuses on the role of tumor budding in invasion and metastasis. Also, we highlight the prognostic significance of tumor budding in HNSCC and its potential for improving clinical decision making in terms of recommending optimal individualized treatment for this patient population.