Higher magnification of the previous image showing poorly-differentiated squamous cell carcinoma with tumor giant cells underneath an uninvolved mucosa. Immunohistochemistry is useful with more poorly differentiated tumors. Squamous cell carcinoma will stain with keratin (intensity of staining depends on the degree of tumor differentiation). Occasional tumors will stain with vimentin. Deletion of A, B, or H blood group has been noted in SCC. Mutation or overexpression of p53 is also usually noted.