All cases had microscopic features within the histologic spectrum of SEF and showed strong and diffuse MUC4 positivity, while lacking SATB2 expression.
Low-grade fibromyxoid sarcoma (LGFMS) and sclerosing epithelioid fibrosarcoma (SEF) are rare tumors with distinct sets of morphological features, both characterized by MUC4 immunoreactivity.
Both neoplasms demonstrated diffuse immunoreactivity for MUC4, a highly specific marker for SEF, and both demonstrated evidence of rearrangement of both the EWSR1 and CREB3L1 genes, which have recently been shown to be fused in this entity.
In reports to date, osteosarcomas are positive for SATB2 and negative forMUC4, whereas soft tissue SEFs have shown the opposite immunohistochemical profile (SATB2-/MUC4+).
We investigated MUC4 expression in SEF and other epithelioid soft tissue tumors to determine (1) the potential diagnostic utility of MUC4 for SEF and (2) the association between MUC4 expression and FUS rearrangement in SEF.