p53, MDM2, bcl-2 staining in follicular neoplasms of the thyroid gland.
Sixty-two follicular adenomas of the thyroid were investigated by immunohistochemistry for the expression of p53, MDM2 and bcl-2 proteins. The wild type of 393 aminoacid nuclear p53 phosphoprotein is the product of a gene located on the short arm of chromosome 17. The p53 protein controls the growth of transformed cells in a culture and thus termed a suppressor gene product. Mouse double minute 2 (MDM2) gene product has been described to occur in malignant epithelial tissue, the protein product of this gene binds to and presumably inactivates the growth suppressive effect of wild type p53 protein. Bcl-2 is an oncogene whose product inhibits apoptosis in many cells types. Some scattered nuclei in two adenomas (3.2%) stained positively for p53. The adenomas with positive staining for p53 were subserially sectioned, but no signs of invasion were found, both patients are alive and well. In 12 adenomas (19%) there was positive reaction for MDM2 protein, whereas none of them where p53 positive. All cases were strongly positive for bcl-2 staining. We conclude that p53 protein expression is not confined to follicular adenomas, while MDM2 and bcl-2 genes products are.