Histopathologic comparison between human oral squamous cell carcinomas and their xenografts in nude mice.

Tumor portions were obtained from 11 oral squamous cell carcinomas and used to produce tumors in a xenogeneic gnotobiotic nude mouse model system. The tumors that developed were examined histologically. The cellular features and tumor growth patterns were compared between the original oral squamous cell carcinoma (T0) and the tumor that developed in the xenogeneic host (T1). The T1 tumors were more highly differentiated in comparison with the T0 tumors. The T1 tumors exhibited less cellular pleomorphism and a more uniform pattern of stratification. The cells in the T1 tumors exhibited an increased mitotic index but did not contain abnormal mitoses. The T1 tumors usually exhibited nodular growth patterns rather than the infiltrating pattern exhibited by the parenchyma of the T0 tumors. The desmoplastic reaction was markedly reduced in the T1 tumors. The results indicated that the gnotobiotic nude mouse model system either selects for or induces a more differentiated pattern of tumor growth than that found in the original human oral squamous cell carcinomas.