CD34 positivity in fibrosarcomas which arise in dermatofibrosarcoma protuberans.

OBJECTIVE: On rare occasion, fibrosarcomatous change may arise in a dermatofibrosarcoma protuberans (DFSP), and this alteration is of prognostic significance. Histologically, this change may be subtle and difficult to recognize. The goal of this study was to evaluate the pattern of CD34 immunoreactivity in DFSP with fibrosarcomatous areas (DFSP-FS). DESIGN: Of 100 cases of DFSP identified at a large metropolitan hospital, 7 were found to have fibrosarcomatous change. Thirty cases of typical DFSP and seven cases of DFSP-FS were stained with an antibody for CD34. RESULTS: All 30 cases of typical DFSP stained intensely for CD34. In the seven cases of DFSP-FS, all cases showed a similar staining pattern in the DFSP portion. However, focal CD34 immunoreactivity was noted in only one (14%) of seven cases in the fibrosarcomatous portion of these tumors. CONCLUSIONS: CD34 immunoreactivity is rare in the fibrosarcomatous portions of DFSP-FS, and this immunophenotype may be diagnostically useful in those cases in which it is difficult to recognize this change histologically.