Early-Stage Oral Squamous Cell Carcinoma in Adolescents and Young Adults Compared with Older Patients Exhibits Distinct Clinicopathological Features

Purpose: This study aimed to compare the clinicopathological features of stage I–II oral squamous cell carcinoma (OSCC) between adolescents and young adults (AYAs) and older patients, and to identify prognostic factors in AYA OSCC. Methods: Forty-eight AYA patients aged 15–39 years and 69 older patients aged ≥ 65 years with surgically treated stage I–II OSCC were retrospectively analyzed. Histological evaluation, survival analysis, immunohistochemistry for p53, p16, and MTAP, high-risk HPV RNA in situ hybridization, and fluorescence in situ hybridization for CDKN2A and MTAP were performed. Results: Compared with older patients, OSCCs in AYAs were more frequently located on the tongue (93.7% vs. 47.8%) and more often exhibited a superficial spreading growth pattern (60.4% vs. 31.8%). AYA tumors more frequently showed modified WPOI-1, high tumor budding, and abnormal p53 immunophenotypes (85.4% vs. 68.1%). AYA patients showed significantly better overall and disease-free survival than older patients. Within the AYA group, depth of invasion (DOI) > 5 mm was associated with distant metastasis and poorer overall and disease-free survival. Postoperative lymph node metastasis occurred in 31.2% of AYAs. Univariable analysis suggested that clinical stage II, tumor thickness > 5 mm, DOI > 5 mm, and tumor budding scores 1–2 were associated with postoperative lymph node metastasis. Molecular status, including p53, p16/CDKN2A, and MTAP, did not provide robust prognostic stratification. Conclusion: Early-stage AYA OSCC exhibits distinct clinicopathological features. DOI was the strongest prognostic indicator, whereas clinical stage, tumor thickness, and tumor budding may provide additional prognostic information regarding the risk of late nodal metastasis.