OBJECTIVETo evaluate the diagnostic criteria and morphologic difference of primary schwannoma from that of soft tissue schwannoma.

METHODSAll neurogenic tumors of the bone in this hospital from 2002 to 2013 were reviewed, four cases of primary schwannoma arising from bone were selected. Their clinical features, radiologic appearance and pathologic findings were evaluated. Immunophenotyping was performed using EnVision method.

RESULTSAll four cases had classic morphologic features and immunophenotype of conventional schwannoma. Compared with schwannoma of the soft tissue, primary bone schwannoma had the following features: benign radiological appearance, absence of capsule under light microscope, local infiltration of bone or destruction of bone cortex, occasionally involving extra-osseous soft tissue. Most tumors were solid, with less cystic degeneration. Histologically, the tumors were mainly composed of compact areas of spindle cells (Antoni A), and areas of hypercellularity could often be observed.

CONCLUSIONSPrimary schwannoma of the bone is rare, usually arises within the long bones and flat bones. Compared to conventional soft tissue schwannoma, it shows different growth pattern, imaging and pathologic features; thus care should be exercised not to misdiagnose schwannoma of the bone as other primary low-grade malignant spindle cell sarcoma of the bone and to avoid unnecessary over-treatment.