CD34 and dermatofibrosarcoma protuberans: Another disease in which FXIII-A has stood the test of time and is used in the diagnosis is dermatofibroma (DF) where the spindle-shaped cells are FXIII-A positive but negative for CD34, in contrast to dermatofibrosarcoma protuberans (DFSP) where the cells are negative for FXIII-A and CD34 positive [53, 54].