MR evaluation of tongue carcinoma in the assessment of depth of invasion with histopathological correlation: A single center experience

Introduction: Magnetic resonance imaging (MRI) has become the cornerstone for pretreatment evaluation of carcinoma tongue and provides accurate information regarding the extent of the lesion and depth of invasion that helps the clinician to optimize treatment strategy. Aim of the study is to correlate MRI and histopathological findings, to evaluate the role of MRI in loco-regional tumor node metastasis (TNM) staging, and to assess the depth of invasion of tongue carcinoma. Materials and Methods: This study was undertaken on 30 patients with clinical diagnosis of tongue carcinoma referred for MR imaging at a tertiary care hospital over the 2-year period between July 2017 and June 2019. MRI was performed with GE 1.5 Tesla scanner, neurovascular (NV) array coil. Clinical and MRI staging of tongue carcinoma was done preoperatively and correlated. Post-surgery, histopathological TNM staging was done and correlated with clinical and MRI TNM staging. The cutoff value of histopathological (HP) depth that could determine the existence of nodal metastasis was 5 mm. Results: In 30 patients diagnosed with tongue carcinoma, the incidence was higher in males (92%). Moderate agreement (k = 0.512) was noted for T staging between clinical and MRI staging assessments. Fair agreement (k = 0.218) was noted for N stage between clinical and MRI staging assessments. There was good agreement (k = 0.871) for M stage between the clinical and MRI staging assessments. Good agreement (k = 0.822 and k = 0.767, respectively) was noted for both T staging and Nstaging between MRI and histopathology staging assessments. The agreement for the T stage was poor (k = 0.012) between the clinical and histopathology staging assessments. Agreement for the N stage was also poor (k = 0.091) between the clinical and histopathology staging assessments. Mean depth of invasion by histology and MRI was 14.22 mm and 16.12 mm, respectively. Moderate agreement (k = 0.541) was noted between clinical and pathological tumor depth and good agreement (k = 0.844) was noted between radiological and pathological tumor depth. As for the T1WGd MRI depth with a cutoff value of 5 mm, the nodal metastasis rate in the group with values >5 mm was 52%, and for those <5 mm was 24%, both of which were significantly different (P = 0.040). Pearson's correlation coefficient of HP depth and T1WGd MRI depth was 0.851 (P < 0.001) suggesting that HP depth shows a strong correlation with T1WGd MRI depth. Conclusion: MRI is the imaging modality of choice for evaluation of tongue carcinoma as MRI helps in accurate staging of the tumor using TNM classification which is crucial for optimizing treatment options. The current study shows a high correlation between MRI and histopathological findings regarding thickness of tumor and depth of invasion. MRI and histopathology assessments of tumor spread were equivalent to within 0.5 mm DOI. Estimation of invasion depth using MRI as a preoperative study in oral tongue carcinoma is essential in planning surgical treatment strategies such as the extent of elective neck dissection. Invasion depth, which greatly affects occult node metastases, must be included in the TNM staging of oral tongue carcinoma.