The pattern of CD-34
antigen (human progenitor cell
antigen) immunoreactivity was studied within normal nerve, and a variety of nerve sheath and
neuroectodermal tumors. Besides normal nerves, 111 soft tissue
tumors were studied, including 17
neurofibromas, 10
neurilemomas, 12
malignant peripheral nerve sheath tumors, 1 melanocytic
schwannoma, 21 fibroblastic lesions, 31 fibrohistiocytic lesions, seven neuroectodermal lesions, and 10 miscellaneous
tumors. CD-34-positive dendritic cells were consistently identified within the endoneurium of normal nerve, all
neurofibromas,
dermatofibrosarcomas, and Antoni B (but not Antoni A) areas of
neurilemomas. CD-34 was not expressed in the majority (eight of 10 cases) of
malignant peripheral nerve sheath tumors. CD-34 was also lacking in all fibroblastic lesions (nodular
fasciitis,
fibromatosis,
keloid,
fibrosarcoma) and in
neuroectodermal tumors that are not generally considered to show true nerve sheath differentiation (neurotropic
melanoma,
clear cell sarcoma, neuroepithelioma). We conclude that CD-34 (or a closely related
epitope) defines a normally occurring nerve sheath cell that appears to be cytologically and immunophenotypically distinct from a fibroblast and conventional Schwann cell. The
antigen can also be localized to benign
nerve sheath tumors, but tends to be lost in malignant ones. The consistent presence of CD-34 within all 13 cases of
dermatofibrosarcoma protuberans can be used as evidence in support of the view that these lesions are variants of
nerve sheath tumors, and distinct from
benign fibrous histiocytomas which consistently lack the
antigen. Finally, expression of CD-34 by one of three
giant cell fibroblastomas reinforces the close relationship between this
tumor and
dermatofibrosarcoma protuberans.