Tumor budding is an independent prognostic marker in early stage oral squamous cell carcinoma: With special reference to the mode of invasion and worst pattern of invasion

Abstract

Pathologically proven regional lymph node metastasis affects the prognosis in early stage oral cancer. Therefore we investigated invasive tumor patterns predicting nodal involvement and survival in patients with clinically node-negative T1 and T2 oral squamous cell carcinoma (cT1,2N0M0 OSCC). Ninety-one cases of cT1,2N0M0 OSCC treated with transoral resection of the primary tumor were assessed based on 3 types of invasive tumor patterns on histopathologic and pancytokeratin-stained immunohistological sections: the mode of invasion, worst pattern of invasion (WPOI), and tumor budding. The correlations among invasive tumor patterns, regional metastasis, and disease-free survival were analyzed. Of the 91 cases, 22 (24%) had pathologically proven regional metastasis. The mode of invasion (p<0.01) and tumor budding (p<0.01) were associated with regional metastasis as well as lymphovascular invasion (p = 0.04) in univariate analysis. In logistic regression analysis, however, tumor budding was the only independent predictor of regional metastasis (hazard ratio (HR) = 3.05, 95% confidence interval (CI) = 0.29-5.30, p<0.01). All three invasive patterns, the mode of invasion, WPOI, and tumor budding, were found to be significant predictors of 5-year disease-free survival (p<0.01, p = 0.03, and p<0.01, respectively) as well as lymphovascular invasion (p = 0.02) and perineural invasion (p = 0.02). A final model for Cox multivariate analysis identified the prognostic advantage of the intensity of tumor budding (HR = 2.19, 95% CI = 1.51-3.18, p<0.01) compared with the mode of invasion and WPOI in disease-free survival. Our results indicate that the intensity of tumor budding may be a novel diagnostic biomarker, as well as a therapeutic tool, for regional metastasis in patients with cT1,2N0M0 OSCC. If the pancytokeratin-based immunohistochemical features of more than five buds, and a grade 4C or 4D mode of invasion are identified, careful wait-and-see follow-up in a short period with the use of imaging modalities is desirable. If there are more than ten buds, a grade 4D mode of invasion, or WPOI-5 in the same section, wide resection of the primary tumor with elective neck dissection should be recommended.

Fig 1. Representative photographs of classification of mode of invasion (H&E staining, immunohistochemical pancytokeratin staining, x40 magnification).

(1A,1B) grade 1, (1C,1D) grade 2, (1E,1F) grade 3, (1G,1H) grade 4C, and (1I,1J) grade 4D.

Fig 2. Representative photographs of classification of worst pattern of invasion (H&E staining, immunohistochemical pancytokeratin staining, x200 magnification).

(2A,2B) Worst pattern of invasion (WPOI)-1, (2C,2D) WPOI-2, (2E,2F) WPOI-3, (2G,2H) WPOI-4, and (2I,2J, x40 magnification) WPOI-5.

Fig 3. Representative photographs of intensity of tumor budding (immunohistochemical pancytokeratin staining, x200 magnification).

(3A) Low intensity of tumor budding (<5 buds), (3B) intermediate intensity of tumor budding (≥5~<10 buds), and (3C) high intensity of tumor budding (≥10 buds).

Fig 4. Photographs of immunohistochemical pancytokeratin staining show representative examples of grade 4D mode of invasion and worst pattern of invasion (WPOI)-4 at x40 magnification.

The region in the rectangle is shown at x200 magnification in the lower panel, which shows 12 buds.

Fig 5. Photographs of immunohistochemical pancytokeratin staining show representative examples of grade 3 mode of invasion and WPOI-5 at x12.5 magnification.

The yellow line measures a distance >1 mm between the main tumor and the next focus of dispersed islands. The region in the rectangle is shown at x200 magnification in the lower panel, which shows 1 bud.

Fig 6. Kaplan-Meier survival curves by mode of invasion (A), worst pattern of invasion (WPOI) (B), tumor budding (C), lymphovascular invasion (D), and perineural invasion (E).

5-year disease-free survivals were 58.0% for grade 1+2+3 mode of invasion, 36.4% for grade 4C mode of invasion, 0.0% for grade 4D mode of invasion (A), 58.4% for WPOI-1+2+3+4, 33.3% for WPOI-5, 65.0% for low-intensity tumor budding (<5 buds), 37.5% for intermediate-intensity tumor budding (≥5 buds-<10 buds), 23.1% for high-intensity tumor budding (≥10 buds), 58.1% for absence of lymphovascular invasion, 33.3% for presence of lymphovascular invasion, 56.1% for absence of perineural invasion, and 20.0% for presence of perineural invsion in patients with clinically node-negative T1 and T2 oral squamous cell carcinoma.

Fig 7. Kaplan-Meier curves of disease-free survival (DFS) in patients in combined groups with the intensity of tumor budding and mode of invasion (A) or worst pattern of invasion (WPOI) (B).

In group A, the 5-year DFSs were 70.4% with low tumor budding and grade 1+2+3 mode of invasion ①, 66.7% with low tumor budding and grade 4C mode of invasion ②, 50.0% with intermediate tumor budding and grade 1+2+3 mode of invasion ③, 0% with intermediate tumor budding and grade 4C mode of invasion ④, 20.0% with high tumor budding and grade 1+2+3 mode of invasion ⑤, 33.3% with high tumor budding and grade 4C mode of invasion ⑥, and 0% with high tumor budding and grade 4D mode of invasion ⑦. In group B, the 5-year DFSs were 72.8% with low tumor budding and WPOI-1+2+3+4 ①, 44.4% with low tumor budding and WPOI-5 ②, 36.4% with intermediate tumor budding and WPOI-1+2+3+4 ③, 60.0% with intermediate tumor budding and WPOI-5 ④, 33.3% with high tumor budding and WPOI-1+2+3+4 ⑤, and 0% for high tumor budding and WPOI-5 ⑥.