Immunohistochemical analysis showed immunoreactivity for MUC4 and break-apart fluorescence in situ hybridization was positive for FUS rearrangement, confirming the diagnosis of LGFMS.
While the majority of LGFMS cases are characterized by a FUS-CREB3L1 fusion, both FUS-CREB3L2 and EWSR1-CREB3L1 fusions were recently demonstrated in a small number of LGFMS and SEF/LGFMS hybrid tumors.
While the majority of LGFMS cases are characterized by a FUS-CREB3L1 fusion, both FUS-CREB3L2 and EWSR1-CREB3L1 fusions were recently demonstrated in a small number of LGFMS and SEF/LGFMS hybrid tumors.
We describe a case of superficial low-grade fibromyxoid sarcoma (LGFMS) in a 12-year-old boy, confirmed by the detection of FUS-CREB3L2 fusion transcripts by reverse-transcription polymerase chain reaction and FUS rearrangement with fluorescence in situ hybridization, which had morphological features similar to ossifying fibromyxoid tumor (OFMT), including an almost complete rim of mature, metaplastic bone.
This fusion has recently been described as a variant translocation in low-grade fibromyxoid sarcoma (LGFMS), a tumor more typically characterized by a recurrent t(7;16) chromosomal translocation, resulting in the fusion of FUS and CREB3L2 genes.
This fusion has recently been described as a variant translocation in low-grade fibromyxoid sarcoma (LGFMS), a tumor more typically characterized by a recurrent t(7;16) chromosomal translocation, resulting in the fusion of FUS and CREB3L2 genes.
Fluorescent in situ hybridization (FISH) with a break-apart probe for FUS revealed the presence of a FUS gene rearrangement confirming the diagnosis of LGFMS.
Our findings therefore expand the spectrum of gene fusions that characterize LGFMS and suggest that the EWSR1 gene may substitute for the function of FUS in gene fusions of sarcoma.
In accordance with previous studies, our case showed positive findings of FUS rearrangement, reinforcing the notion of a close relationship between low grade fibromyxoid sarcoma and SEF.
We evaluated cases of pure sclerosing epithelioid fibrosarcoma lacking areas of low-grade fibromyxoid sarcoma for FUS rearrangement to determine whether this entity could be related to low-grade fibromyxoid sarcoma.
We present a case of an ossifying tumor of the perineum that required an open biopsy and fluorescent in situ hybridization testing for FUS and CREB3L2 for diagnosis as a variant of low-grade fibromyxoid sarcoma.
FUS-CREB3L2 was capable of activating transcription from CD24 regulatory sequences in luciferase assays, suggesting an important role for the upregulation of this gene in LGFMS.