Immunohistochemical staining with the same antibody on the tumor sections showed that while p53 was undetectable in both MMTV-Hras/p53+/+ and MMTV-Hras/p53-/- tumors, the MMTV-Hras/p53R172H/R172H tumors displayed a relatively uniform, high level of p53 in the nucleus of tumor cells, but not in the adjacent stromal cells (Fig. 3B). This evidence concerns the gene TP53 and neoplasm.