Morphometric grading of squamous cell carcinoma.

Histological grading of squamous cell carcinoma is subjective and suffers from poor observer reproducibility. We investigated the feasibility of quantifying histological differentiation via point counting, using both the degree of keratinization and a novel definition of differentiation that was based on architectural features of the tumour. Multiple recounts of 20 cases of human oral squamous cell carcinoma were performed at several magnifications (X100, X160 and X250). Six lines of human squamous cell carcinoma tumour lines were examined for changes in differentiation following transplantation to athymic nude mice. Observer reproducibility was extremely high for all recounts except at the highest magnification, where the tumour architecture may have been obscured. Of the human squamous cell carcinomas transplanted to nude mice, five of six tumour lines showed significant histological changes, most commonly toward decreased differentiation. The changes were usually present in the initial transplant and were similar to those we have reported for transplants of adenocarcinomas. We conclude that histological differentiation can be quantified in squamous cell carcinomas with a high degree of observer reproducibility, even in the absence of keratinization; the method employed is sufficiently sensitive to be applied to practical problems of biological significance.