The immunoexpression of bcl-2 and p53 in Kaposi's sarcoma.

The aim of this study was to examine the immunohistochemical expression of p53 and bcl-2 in Kaposi's sarcoma and relate this with proliferation index (as measured by MIB-1 staining) and clinicopathological subtypes. Twenty formalin-fixed, paraffin-embedded cases of Kaposi's sarcoma were stained with commercially available antibodies to p53, bcl-2 and MIB-1, after pressure cooking antigen retrieval. All cases were strongly positive for bcl-2 with the majority containing more than 75% positive cells. In comparison, p53 expression was less striking. Eleven cases contained less than 24% (+1) of cells staining positively. Only two cases showed greater than 75% of positive cells, and both of these latter two lesions had metastasized. The MIB-1 staining in all cases of Kaposi's sarcoma was strongly positive, irrespective of clinicopathological type, in keeping with the highly proliferative nature of this lesion. Thus, we have demonstrated uniformly increased expression of bcl-2 protein in Kaposi's sarcoma irrespective of clinicopathological subtype and MIB-1 staining, while p53 expression is relatively less common, except in those cases which have metastasized. This may help identify those cases that will behave in a more aggressive manner. However, more cases need to be evaluated to verify this.