In addition to an absence of tumour induction, Apc-null pituitaries do not display the microenvironmental alterations that usually precede tumour growth, such as the aberrant expression of ECM markers or the recruitment of a population of proliferating non-oncogene targeted (YFP-negative) endothelial-like cells expressing SOX9 (Fig. 5c). Here, SOX9 is linked to neoplasm.