A NOVEL PANEL OF ANTIBODIES THAT SEGREGATES IMMUNOCYTOCHEMICALLY POORLY DIFFERENTIATED CARCINOMA FROM UNDIFFERENTIATED CARCINOMA OF THE THYROID-GLAND

The expression of bcl-2 and p53 was investigated by immunocytochemistr y in combination with that of conventional structural and differentiat ion antigens on the archival material of 22 cases of undifferentiated carcinoma (UC) and 19 of poorly differentiated carcinoma (PDC) of the thyroid gland. The restriction of bcl-2 expression to PDC in compariso n to UC was 84.2% versus 13.6% of cases, respectively, in contrast to an almost equal percentage of p53 expression in the two histologic typ es, that is, 52.6% and 54.5% of cases of PDC and UC, respectively. How ever, the pattern of distribution of p53-immunoreactive cells was defi nitely different, being restricted to areas showing active infiltratin g growth in PDC and involving almost all tumor cells in UC. Furthermor e, in the subset of cases of UC showing the residual presence of a dif ferentiated component, a distinctive mutual exclusion of bcl-2 and p53 immunoreactivity was observed in the two components. The results sugg est that the evaluation of bcl-2 expression may be usefully applied to the differentiation of PDC from UC, whereas all morphologic findings related to p53 expression are in keeping with a significant role of th e deregulation of this gene in the mechanism of dedifferentiation and progression of the disease.