title: Low-grade fibromyxoid sarcoma mimicking solitary fibrous tumor: a report of two cases.
abstract: Low-grade fibromyxoid sarcoma (LGFMS) is an uncommon fibroblastic neoplasm with many morphologic mimics. Solitary fibrous tumor is a more common fibroblastic neoplasm, but the two rarely enter the same differential diagnosis. However, here, we report two unusual cases of LGFMS, containing dilated, hemangiopericytoma-like blood vessels, which prompted diagnostic considerations of solitary fibrous tumor. Both cases presented were confirmed to harbor FUS gene rearrangement, thereby confirming a diagnosis of LGFMS. One case is that of an 18-year-old male with a left forearm mass, and the other a 50-year-old man with a left popliteal mass. While both cases show some histologic features of LGFMS, the non-classical, dilated blood vessel pattern seen here may serve as a diagnostic pitfall, as LGFMS normally exhibits fine, curvilinear blood vessels. To our knowledge, there is only one other report of LGFMS displaying such hemangiopericytoma-like blood vessels. In summary, when encountering a bland spindle cell neoplasm with classic hemangiopericytoma-like blood vessels, it is prudent to consider a diagnosis of LGFMS besides solitary fibrous tumor--particularly in the absence of CD34 immunoreactivity as it may be a rare, mimicking variant of LGFMS.
authors.affiliation: Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada.
authors.forename: Sylvia
authors.initials: S
authors.lastname: Papp
authors.forename: Brendan C
authors.initials: BC
authors.lastname: Dickson
authors.forename: Runjan
authors.initials: R
authors.lastname: Chetty
mesh_terms: D000293:Adolescent; D014408:Biomarkers, Tumor / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D003937:Diagnosis, Differential; D005350:Fibroma / Q000175:diagnosis* / Q000235:genetics; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D008297:Male; D008875:Middle Aged; D012509:Sarcoma / Q000175:diagnosis* / Q000235:genetics; D012983:Soft Tissue Neoplasms / Q000175:diagnosis* / Q000235:genetics; D054364:Solitary Fibrous Tumors / Q000175:diagnosis* / Q000235:genetics; D025521:Tumor Suppressor Proteins / Q000235:genetics
chemical_list: D014408:Biomarkers, Tumor; C499993:TUSC2 protein, human; D025521:Tumor Suppressor Proteins