Bcl-2 and p53 expression in insular and in well-differentiated thyroid carcinomas with an insular pattern.

Expression of p53 and bcl-2 oncogenes was investigated in poorly differentiated, so-called insular carcinomas of the thyroid gland and also in the follicular and papillary carcinomas with an insular component. Hematoxylin-eosin sections of 217 thyroid carcinomas were reevaluated for insular carcinoma and also for thyroid carcinomas with an insular component. Immunohistochemical staining method was used for detecting p53 and bcl-2 expression on paraffin blocks of three pure insular, five follicular or papillary thyroid carcinomas with a major insular component (more than 50%) and six with a minor insular component (20-50%). Flow cytometry was also performed in these cases. None of the cases showed p53 immunoreactivity. Bcl-2 expression was observed in all cases and the most intense staining was seen in insular areas. All the cases were diploid. We suggest that bcl-2 plays a role in loss of differentiation of thyroid carcinomas.