[Ultrasonographic diagnosis of tongue cancer using intraoral high frequency probe]

Recent progress in ultrasonography has enabled to provide high-resolution images of superfical regions. In this study, the usefulness of ultrasonography using a high frequency probe for squamous cell carcinoma of the tongue was evaluated. Thirty normal adult subjects were examined to study ultrasonographic findings of normal tongue. The pattern of the normal tongue showed clearly three different zones, corresponding to three layers; mucosal epithelium, proper lamina and tongue muscle. The mean and standard deviation of epithelium thickness was 2.1 +/- 0.6 mm. The ultrasonographic findings for tongue carcinoma in 104 patients were evaluated. The ultrasonographic pattern of tongue carcinoma showed a hypoechoic structure as compared with surrounding tongue muscle. Depth of invasion defined as the distance between normal mucosal surface and the deepest point in 59 patients was measured. The mean and standard deviation of depth of invasion measured by ultrasonography was 8.1 +/- 4.0 mm. The depth of invasion increased with T-stage. The difference of tumor depth between T1 and T2, or T1 and T3 was statistically significant (p < 0.001). A significant correlation (p < 0.001) was obtained between depth of invasion measured by ultrasonography and that measured by histological sections. In the group of patients with the tumor depth exceeding 8 mm (mean depth), the lymph node metastasis rate was 75.0% (15/20). In the group of patients with the depth of less than 8 mm, the incidence of metastasis was 29.8% (14/47). The difference between the two groups was statistically significant (p < 0.001). The 5-year survival rate calculated by the Kaplan-Meier method was 45.7% in patients with the depth exceeding 8 mm and was 87.5% in patients with the depth of less than 8 mm. The difference was statistically significant (p < 0.001). In conclusion, ultrasonography using a high-resolution probe was very useful for evaluation of squamous cell carcinoma of the tongue, and depth of invasion measured by ultrasonography could be a predictive factor for cervical lymph node metastasis and patient survival rate.