[Plexiform fibrohistiocytic tumor of soft tissues and bone].

Plexiform fibrohistiocytic tumor is a rare lesion which has been reported only in the dermis and subcutis so far. We present two cases in this location and an additional one localized in the proximal epiphysis of the tibia. A case with crural location showed predominance of plexiform tumorous nodes with fibrohistiocytic arrangement. The nodes were composed of spindle-shaped myofibroblasts with admixture of histiocytes and giant multinucleated osteoclast-like cells. In another case the tumor of axillary soft tissues featured mostly plexiform bundles of spindle-shaped myofibroblast-like cells reacting positively with actin and CD 68 antibodies; ultrastructurally, they contained numerous dense lysosomal inclusions with myelin figures. The bone tumor was composed of hyalinized fibroblastic component with disperse fibrohistiocytic nodes. Despite a semimalignant character of the lesion there was no recurrence in our cases during the 2-6 year postoperative period.