Depth of invasion as a predictive factor for cervical lymph node metastasis in tongue carcinoma

Many histopathologic parameters in head and neck squamous cell carcinoma have been identified as predictive factors for cervical metastasis. Several studies focused on tumor thickness, and the depth of invasion was suggested to have a relationship to the occurrence of cervical metastasis. Nonetheless, the criterium for elective neck therapy in terms of tumor depth is still inconclusive. Therefore, a retrospective study was undertaken to substantiate the differing results in the literature with our own findings concerning the interrelationship between tumor thickness and clinically suspicious neck, as well as occult neck disease. In addition, the study attempted to identify further predictive factors for cervical metastasis in squamous cell carcinoma of the tongue.

The medical records of 34 primary tongue carcinomas operated without any preoperative therapy between 1980 and 1991 were reviewed. Each patient's tumor type, tumor location, tumor size, invasion mode, depth of invasion, intralymphatic tumor emboli, and perineural invasion were evaluated. Chi-square contingency tables were used to correlate clinical or histopathologic parameters with metastasis in the neck.

The overall cervical metastatic rate was 35.3% (n = 12/34). In univariate analysis, invasion mode and depth of invasion were statistically significant predictors of regional metastasis at p = 0.0019 and p = 0.0003, respectively. In the group in which tumor depth exceeded 5 mm, the metastatic rate was 64.7% (11/17). In contrast, when the depth of invasion was less than 5 mm, the incidence of cervical metastasis was 5.9% (1/17). Clinically negative necks turned out pathologically positive in 30.0% (n = 9/30). The tumor depth exceeded 5 mm in 43.4% (13/30) of the N0 necks. In the conversion (N0-->N1) group, tumor depth exceeding 5 mm was noted in 88.9% (n = 8/9).

We suggest that there is a discerning point at 5 mm of tumor depth at which cervical metastasis is probable. Electric neck therapy (surgery or irradiation) is strongly indicated for tumors exceeding 5 mm invasion. Tumor invasion mode and tumor size also bear an impact on the indication for therapy.