CD34 AND FACTOR-XIIIA IN THE DIFFERENTIAL-DIAGNOSIS OF DERMATOFIBROMAAND DERMATOFIBROSARCOMA PROTUBERANS

To assess the use of anti-CD34 and anti-factor-XIIIa antibodies for th e differential diagnosis of dermatofibroma (DF) and dermatofibrosarcom a protuberans (DFSP), we stained 40 DFs and 13 DFSPs. A significant po pulation of dendritic and spindle cells was reactive with anti-factor- XIIIa in 90% of DFs. In DFSP, most cases had very few or no reactive c ells for this antiserum and reactivity was confined to the infiltratin g edges of the neoplasm or to a very low percentage of cells within th e bulk of the tumor. A significant overlap was detected, a reason why the stain is useful but lacks absolute specificity for this purpose. H uman progenitor cell antigen (CD34) was found in all cases of DFSP tha t had 50-100% of reactive cells, but in only five DFs. In DFs, the rea ctivity for CD34 was focal, with only less-than-or-equal-to 20% positi ve cells. When used together with other histopathological criteria, fa ctor-XIIIa antibody and particularly CD34 may help to differentiate th ese two processes.