Immunohistochemical analysis showed immunoreactivity for MUC4 and break-apart fluorescence in situ hybridization was positive for FUS rearrangement, confirming the diagnosis of LGFMS.
Low-grade fibromyxoid sarcoma (LGFMS) and sclerosing epithelioid fibrosarcoma (SEF) are rare tumors with distinct sets of morphological features, both characterized by MUC4 immunoreactivity.
Hyalinized spindle cell tumor with giant rosettes (HSCTGR) is a morphological variant of LGFMS that shares the same balanced translocation, and is also immunoreactive for MUC4.
MUC4 has recently been identified as a sensitive and specific marker for LGFMS; MUC4 expression was also observed in 2 tumors with hybrid features of SEF and LGFMS.
Gene expression analysis clearly distinguished LGFMS from morphologically similar tumors and MUC4 was identified as a potential diagnostic marker for LGFMS by gene expression and IHC analysis.