FUS rearrangements are rare in 'pure' sclerosing epithelioid fibrosarcoma

Several recent reports have described low-grade fibromyxoid sarcoma with sclerosing epithelioid fibrosarco-ma-like areas. We evaluated cases of pure sclerosing epithelioid fibrosarcoma lacking areas of low-gradefibromyxoid sarcoma for FUS rearrangement to determine whether this entity could be related to low-gradefibromyxoid sarcoma. Available formalin-fixed paraffin-embedded tissue of 27 sclerosing epithelioidfibrosarcoma from 25 patients was retrieved and tabulated with clinical information. Unstained slides fromformalin-fixed paraffin-embedded blocks were prepared and fluorescence in-situ hybridization was performedusing a commercial FUS break-apart probe. The median patient age at presentation was 50 (range, 14–78) years,with 14 males and 10 females. Sclerosing epithelioid fibrosarcoma most commonly involved the extremities(n¼8) or chest (n¼6). Sixteen patients had a median follow-up of 17 (range, 1–99) months; seven were alive andwell at 12 (range, 5–30) months; three alive with disease at 28 (range, 9–99) months; five dead of disease at amedian of 22 (range, 1–36) months and one was dead of unknown causes. Twelve patients were known to havemetastases; the most common site was lung (n¼7), followed by bone (n¼3), lymph nodes (n¼2) andperitoneum (n¼1). Only 2 of 22 (9%) analyzable cases of sclerosing epithelioid fibrosarcoma showedrearrangement in the FUS locus by fluorescence in-situ hybridization. Although cytogenetically confirmed low-grade fibromyxoid sarcoma can have sclerosing epithelioid fibrosarcoma-like areas, FUS rearrangement, whichis characteristic of low-grade fibromyxoid sarcoma, appears to be relatively rare in pure sclerosing epithelioidfibrosarcoma.Modern Pathology advance online publication, 2 March 2012; doi:10.1038/modpathol.2011.214Keywords: FUS; low-grade fibromyxoid sarcoma; sclerosing epithelioid sarcoma