The study was carried out by immunocytochemistry on archival material using antibodies against bcl-2 and p53 protein on tissue sections of 40 adenomas (As), 20 medullary carcinomas (MCs), 70 well-differentiated carcinomas (WDCs), 20 poorly differentiated carcinomas (PDCs) and 24 undifferentiated carcinomas (UCs). This evidence concerns the gene TP53 and undifferentiated carcinoma.