Objective To determine the correlation between the radiologic magnetic resonance imaging (MRI) depth of invasion (MRI-DOI) and pathologic depth of invasion (p-DOI) in oral cavity primary tongue squamous cell carcinoma (TSCC).

Methods Fifty-two cases of pathologically proven primary TSCC were selected from patients admitted to The Ninth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine between January 2015 and December 2018. The p-DOI was measured, and the relationship between p-DOI and patients’ clinicopathological parameters and prognosis were analyzed. The MRI-DOI was retrospectively measured, and the correlation between MRI-DOI and p-DOI was investigated.

Results Among the 52 patients, the average p-DOI was (8.5±5.5)(1-30) mm. p-DOI was significantly correlated with tumor size (P=0.021) and tumor site (P=0.047) when p-DOI was >5 mm, and significantly correlated with level Ⅲ lymph node metastasis (P=0.01) when p-DOI was≥10 mm. A close relationship between p-DOI>7 mm and the patient 5-year survival was also demonstrated (P=0.048). The average MRI-DOI was (10.3±4.3) mm, with a maximum of 19.9 mm and a minimum of 3.1 mm. The MRI-DOI≥10 mm also predicted poor survival in patients with TSCC (P=0.043). The MRI-DOI measured was generally slightly higher than p-DOI, with an average difference of 1.94 mm, and a strong correlation was found between MRI-DOI and p-DOI (r=0.831, P<0.001).

Conclusions MRI-based radiologic DOI measurement was useful in estimating postoperative p-DOI, and may help predict the depth of invasion of tumors preoperatively, which has important reference value for treating primary TSCC.