The role of Depth of Invasion as a prognostic factor in Oral Squamous Cell Carcinoma

Oral squamous cell carcinoma (OSCC) is a neoplasm that originates from the epithelial mucosa of oral cavity. More than 90% of carcinomas of the oral cavity are Squamous Cell Carcinoma (SCC). Tobacco, alcohol and HPV are considered to be the primary risk factors. The most common intra-oral site for head and neck cancers is the tongue. Neck nodal metastasis has been established as the predictor of survival for oral cavity tumors. Neck dissection is mandatory if the risk of nodal metastasis is >15-20%. Tumor Thickness ( TT ) and Depth of Invasion (DOI) represent the most important prognostication in terms of loco-regional control and survival. It also helps to assess Disease-Specific Survival (DSS). Aims and Objectives: The aim of the study was to assess the risk of neck nodal metastasis in relation to DOI, and to find out its diagnostic and prognostic implications in different intra-oral lesions. Materials and methods: We have studied 140 patients with suspected intra-oral SCC having lesions in mucosal lip, buccal mucosa , floor of the mouth, hard palate and anterior 2/3rd of tongue. Ocular micrometer was used to measure depth of invasion Results: Among 140 patients, 80.0% of the cases were moderately differentiated squamous cell carcinoma. The optimal cut-off value of DOI in discriminating lymph node metastasis from non-lymph node metastasis was found to be 9.1 mm. Lymph node metastasis was found more often in patients with DOI ≥ 5mm. Conclusion: The depth of invasion is the strongest histological predictor of metastatic tumour growth, according to the recent AJCC pT classification