New observations on three cases of ossifying fibromyxoid tumor of soft parts.

Three cases of a recently established entity named "ossifying fibromyxoid tumor of soft parts" (OFMT) were studied histologically, ultrastructurally and by immunohistochemistry. All three tumors were stated in women from 48 to 54 years of age. One tumor was situated superficially in the skin and subcutaneous tissue. Other two tumors were deep-seated, with more diffuse and abundant ossification also in tumor free parts. In one of cases radiological and histological signs of chondroosteosarcomatous features in the ossifying parts of the tumor were stated. In two cases histologically and ultrastructurally multinucleated, vimentin and S-100 protein positive "fibroblastoid" cells were found. The histological and electron microscopic investigations did not rule out the possibility that the tumor cells have also potential properties of osteoblasts, but on the basis of histological, ultrastructural and immunohistochemical data it seems that these tumors are of mesenchymal multipotential derivatives of fibroblastoid origins.