Staging significance of bone invasion in small-sized (4 cm or less) oral squamous cell carcinoma as defined by the American Joint Committee on Cancer

•We examined a large group of patients with oral squamous cell carcinoma.•In all cases, bone invasion was significantly associated with disease progression.•However, in small tumors, bone invasion was not a significant prognostic factor.•But both buccal and lingual bone invasion was an independent prognostic factor.•These significant results are consistent with American Joint Committee on Cancer.

SummaryObjectivesThe staging significance of bone invasion is controversial in oral squamous cell carcinoma (OSCC) cases with tumors measuring 4 cm or less according to the American Joint Committee on Cancer (AJCC). Our aim was to retrospectively examine a large group of patients with OSCC to determine the staging significance of bone invasion.Materials and MethodsThree hundred and twenty-three patients with primary OSCC were classified based on tumor size. Bone invasion was categorized as absent, one side bone, and both buccal and lingual bones, and analyzed for association with disease progression. Regional lymph node metastasis (N), perineural invasion, vascular invasion, surgical margin involvement, and adjuvant treatment were also analyzed.ResultsIn all OSCC cases, bone invasion (p = 0.007) with stage N, perineural invasion, and surgical margin involvement were significant independent prognostic factors of disease progression. However, in OSCC cases with tumors measuring 4 cm or less, bone invasion was not significantly associated with disease progression. Nevertheless, invasion of both buccal and lingual bones was significantly associated with disease progression (p = 0.03). In multivariate analysis, both buccal and lingual bone invasion (p = 0.04; hazard ratio = 3.4; 95% confidence interval, 1.0–11.0), stage N2, and perineural invasion were also independent prognostic factors.ConclusionAlthough OSCC bone invasion was an independent prognostic factor, bone invasion in small OSCC was not. However, small OSCC with both buccal and lingual bone invasion had a significantly worse prognosis. The AJCC T system is of limited prognostic value for small OSCC with bone invasion. But other elements should be examined before a modification can be accepted.