Role of MRI in the Assessment of Depth of Invasion of Oral cavity Squamous Cell Carcinoma with Histopathological Correlation: A Prospective Diagnostic Validation Study

Background Oral cavity squamous cell carcinoma (SCC) is responsible for 84% to 97% cases, with most common site being mobile tongue, buccal mucosa, floor of mouth and lip. The main alterations in 8th edition of AJCC for oral cavity SCC were addition of depth of invasion (DOI) of primary tumor in T category, and extra-nodal extension (ENE) in N category. Numerous studies have shown that the risk of neck lymph node metastasis increases apparently when the pathologic DOI is greater than 4.0 mm. Our study was first prospective study from North India in which 90 patients of oral cavity SCC were enrolled, after introduction of 8th edition of AJCC staging system. In these patients, diagnostic validation of MRI was done in assessment of DOI of oral cavity SCC, and these results were compared with histopathology, after surgery. Aim and Objective To determine the role of MRI in assessment of DOI of Oral Cavity SCC. Material and Method This prospective, cross-sectional study was conducted in a tertiary care hospital in North India, after Institutional Ethical Clearance, with 90 patients enrolled over a period of 18 months. All the patients fulfilling the inclusion criteria was subjected to thorough history, including chief complaint, smoking history, family history, and thorough clinical examination, followed by MRI scan. Observation and Result There were 78 male and 12 female patients, with age ranging from 27 to 83 years. Tongue (67), followed by buccal mucosa (22) and floor of mouth (1) were the most commonly involved primary site in oral cavity SCC. All patients had surgical resection with curative intent, based on appropriate clinical assessment and MRI staging. There was a strong correlation between DOI (mm) (HPE) and DOI (mm) (MRI), for both subsite tongue and subsite buccal mucosa, which was statistically significant. Mean DOI by histopathology and MRI was 16 mm and 17 mm respectively. Strong correlation was found between the MRI and pathological staging, in T stage assessment, N stage assessment and tumor stage assessment. Near perfect agreement was seen between two methods, which was statistically significant. Conclusion MRI is a highly accurate, preferred imaging modality for preoperative assessment of oral cavity SCC, especially for determining the true DOI. In summary, using MRI to estimate invasion depth before surgery, is crucial in planning appropriate treatment strategies for oral cavity SCC, especifically in determining the extent of elective neck dissection. It ensures more accurate and effective surgical planning, and helps in achieving optimal outcome for patients.