To examine the p53 expression in cancer development, we studied the case of a 59-year-old male suffering from squamous cell lung cancer. He was submitted to surgery for resection of the tumoral mass. Through immunoblot and immunohistochemical analysis, the tumor fragment was shown to bear p53 and hsp70 accumulation not detected in the normal lung tissue sample. Six months later, immunohistochemical analysis of a biopsy sample taken from the previous tumor site showed p53 accumulation. Considering the high specificity for p53 detection (100%), this result suggests probable tumor reincidence, not detected by the ordinary H&E staining.