A Basaloid nests displaying central necrosis without keratinization. B Basaloid cell nests showing an irregular lobular pattern of growth with a focal squamous differentiation (arrow). C Immunohistochemical stain with Ki-67/Mib1 showing strongly positive tumour cells at the periphery of the nest. D Basaloid nest showing p27kip1 positive staining tumour cells toward the central of the nest, whereas the cells at the invading front of the tumour are negative. E p27kip1 positive staining in the areas of squamous cell differentiation.