CAL 27 is one of the most frequently used cell lines in the field of oral squamous cell carcinoma (OSCC) studying. However, our recent studies showed that the growth pattern of CAL 27 xenograft did not seem like typical OSCC. In this study, we verified the identity of CAL 27 cells by using by short tandem repeat analysis. Then, we performed tumor formation assay, HE staining and immunohistochemistry assay to further study the growing characteristics and histopathological diagnosis of CAL 27 xenografts. Our results showed that CAL 27 xenografts grew slowly in vivo with vesicle formation at both the surfaces and deeper areas of the tumors. The CAL 27 xenografts were then diagnosed as oral adenosquamous carcinomas. Thus CAL 27 appears to be an oral adenosquamous carcinoma cell line.