CD34 immunoreactivity distinguishes between scar tissue and residual tumor in re-excisional specimens of dermatofibrosarcoma protuberans.

Dermatofibrosarcoma protuberans (DFSP) is a locally aggressive tumor that often recurs after simple excision, and therefore usually requires wide surgical re-excision. It is sometimes difficult to distinguish histologically between residual tumor and scar tissue formed in response to the original biopsy. In an effort to solve this diagnostic problem, we have examined CD34 immunoreactivity in 10 primary biopsies of DFSP, 12 scars, and 7 re-excisional DFSP specimens containing residual tumor adjacent to scar tissue. In all 10 primary biopsies of DFSP, the tumor cells strongly and uniformly expressed CD34. In the 12 scars, only periadnexal cells, endothelial cells, and rare, scattered dendritic cells in the dermis were immunolabeled for CD34. In the 7 re-excisions of DFSP, the foci of residual DFSP were strongly immunolabeled, while the surrounding scar tissue was not. The pattern of CD34 immunoreactivity distinguishes DFSP from scar tissue, and thereby may permit more accurate assessment of surgical margins in re-excisional specimens of DFSP.