Background: The histologic grading of the deep invasive margin of oral squamous cell carcinoma recently has been shown to have prognostic value, but previous series have not been homogeneous enough to allow grading parameters to be assessed individually.
Methods: Forty-seven small lingual carcinomas limited to the lateral border of the tongue and treated by radiotherapy were graded histologically at their deep invasive front. Clinical and grading parameters were correlated by statistical tests performed by permutational techniques.
Results: Carcinoma recurred locally in 6 patients, and metastases developed in 19. Local recurrence correlated with Broders' grade (P = 0.0143), keratinization (P = 0.017) and pattern of invasion (P = 0.0195). Metastasis had a highly significant correlation with Broders' grade (P < 0.001), pattern of invasion (P < 0.001), and invasive front grading total score (P < 0.001). Seven of 8 carcinomas with diffuse infiltrating patterns metastasised, whereas only 4 of 25 with large islands or a broad infiltrating pattern metastasized.
Conclusions: The usefulness of the deep invasive front grading system for small lingual carcinoma was demonstrated. The pattern of invasion was the component of the grading system that had the closest correlation with metastasis and recurrence in this type of carcinoma.