[72] Malignant Fibrous Histiocytoma and Fibrosarcoma of Bone in 2011: What's New?

Salvatore Romeo, Judith VMG Bovee, Irene Carraretto, Roberto Tirabosco, Cristina Natali, Herman M Kroon, Lucia Zanatta, Raf Sciot, Fredrik Mertens, Nicholas Athanasou, Marco Alberghini, Pancras CW Hogendoorn, Angelo P Dei Tos. Treviso Regional Hospital, Treviso, Italy; Leiden University Medical Center, Netherlands; Royal National Orthopaedic Hospital, London, United Kingdom; Rovigo Regional Hospital, Rovigo, Italy; Leuven University, Netherlands; Lund University Hospital, Lund, Sweden; Nuffield Orthopaedic Center, Oxford, United Kingdom; Rizzoli Orthopaedic Institute, Bologna, Italy

Background: Malignant fibrous histiocytoma (MFH) and fibrosarcoma (FS) of bone are rare primary malignant bone tumors and contentious entities. Cases diagnosed as bone MFH and FS were retrieved from the archives of 5 bone tumor referral centers and reviewed to determine whether recent advances in immunohistochemistry together with new tumor classification allowed for reclassification and identification of histologic subgroups associated with distinct clinical behavior.
Design: Tumors originally diagnosed as MFH (n= 51) and FS (n=9) of bone were collected within EuroBoNeT, a European Commission-funded network of excellence for the study of the pathology and biology of bone tumors. A panel of immunostains was applied to each case including: SMA, desmin, H-caldesmon, CKAE3-1, CD31, CD34, CD68, CD163, CD45, S100, and EMA. Additional FISH and immunohistochemical analyses were performed, when appropriate, to confirm/reject alternative diagnoses. All cases were reviewed by 6 experienced bone pathologists; in discrepant cases a consensus was reached at a joint microscopy session.
Results: After morphologic, immunohistochemical and radiologic analyses, seven cases were reclassified as leiomyosarcoma, one as spindle cell rhabdomyosarcoma, three as myxofibrosarcoma and five as osteosarcoma. Among the remaining 44 cases we identified 5 subgroups. Four were reclassified as spindle cell sarcoma not otherwise specified and their morphology corresponded well with the previous description for bone FS. Seven cases were reclassified as undifferentiated pleomorphic sarcoma (UPS) and 10 as UPS with incomplete myogenic differentiation, due to positivity for at least one myogenic marker. Among the remaining 23 cases we identified a further two recurrent morphologic patterns: 8 cases demonstrated a myoepithelioma-like phenotype, while 15 cases displayed a myofibroblastic phenotype.
Conclusions: In a substantial number of cases the diagnoses were changed due to new immunohistochemical markers and revised diagnostic criteria. Five subgroups were identified in the remaining cases. In parallel to previous data on soft tissue MFH, identification of these subgroups may be prognostically relevant.
Category: Bone & Soft Tissue

Monday, February 28, 2011 9:15 AM

Platform Session: Section F, Monday Morning

 

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