A methodologic study of histologic classification and grading of malignancy in oral squamous cell carcinoma.

A multifactorial grading system was devised for the histologic classification and grading of malignancy in carcinoma of tongue and floor of mouth. The system is presented with all morphologic variables defined and illustrated. Statistical analysis of the classification of 52 cases of squamous cell carcinoma revealed that the reproducibility of the system by two independent observers was good for all morphologic variables. Mean total malignancy, tumor cell population, and tumor-host relationship scores showed statistically significant correlations with mean ratings for all the different morphologic parameters, with certain specified exceptions. Reasons for the exceptions and lack of correlation of the histotechnical and theoretical errors of previous grading systems are explored.