Interphase FISH using this newly developed probe is sensitive and specific for detecting the EWS gene on FFPE tissues and is of value in the routine clinical diagnosis of ES/PNET, DSRCT, and CCS.
Recurrent gene fusions involving EWSR1 with members of the cAMP response element binding protein (CREB) family (ATF1 and CREB1) have been reported in a diverse group of tumors including angiomatoid fibrous histiocytoma (AFH), soft tissue and gastrointestinal clear cell sarcoma, primary pulmonary myxoid sarcoma, and hyalinizing clear cell carcinoma of salivary gland.
In Ewing's sarcoma and malignant melanoma of soft parts, translocations of band 22q12 to chromosome 11 and 12 result in the fusion of EWS with the transcription factors FLI-1 and ATF1, respectively.
Bilateral salpingo-oophorectomy was performed and the light microscopic and immunohistochemical findings coupled with the detection of an EWSR1 rearrangement by fluorescence in situ hybridization were compatible with a diagnosis of CCSST metastases to the ovaries.
The sequencing of obtained fragments revealed the presence of a novel chimerical transcript-the in-frame fusion between EWSR1 exon 7 and ATF1 exon 6 that represents the fourth in-frame type of EWSR1/ATF1 fusion identified in clear cell sarcomas.
Clear cell sarcoma (CCS) of tendons and aponeuroses, also known as melanoma of soft parts, represents an aggressive rare malignancy that is characterized by a nested or fascicular pattern of spindled cells and a pathognomonic reciprocal translocation, t(12;22)(q13;q12), that results in the fusion of EWSR1 and ATF1 genes.
RT-PCR and sequence analysis revealed the presence of a fusion transcript bringing together exon 7 of EWS with exon 5 of ATF1, consistent with a type 2 transcript reported in association with CCS.
EWSR1 rearrangements were first identified in Ewing sarcoma, but the spectrum of EWSR1-rearranged neoplasms now includes many soft tissue tumour subtypes including desmoplastic small round cell tumour (DSRCT), myxoid liposarcoma (MLPS), extraskeletal myxoid chondrosarcoma (EMC), angiomatoid fibrous histiocytoma (AFH), clear cell sarcoma (CCS) and myoepithelial neoplasms.
The different translocation partners of the EWS gene, all of which are putative or definite transcription factor genes, may be responsible for the biological differences between DSRCT, Ewing's sarcoma, and clear cell sarcoma.
In this study, we performed mutation analysis of BRAF and NRAS, investigated the EWSR1 gene rearrangement and evaluated the protein expression of insulin-like growth factor 2 and insulin-like growth factor 1R in 31 cases of malignant melanoma and 16 cases of clear cell sarcoma.
Gene fusions of Ewing sarcoma breakpoint region 1 (EWSR1) with members of the cAMP response element-binding protein family (CREB) of transcription factors (CREB1, activating transcription factor 1 (ATF1), and cAMP response element modulator (CREM)) have been described in histopathologically diverse mesenchymal neoplasms such as AFH, hyalinising clear cell carcinomas of salivary glands, primary pulmonary myxoid sarcoma, and clear cell sarcoma.
Rearrangements of the EWSR1 gene are found in an increasing number of human neoplasms, including several tumors that can involve the skin: Ewing sarcoma/primitive neuroectodermal tumor, angiomatoid (malignant) fibrous histiocytoma, myoepithelioma of soft tissue, and clear cell sarcoma.
Clear cell sarcoma (CCS) of soft tissue is a rare sarcoma with morphologic similarities to malignant melanoma but a distinct genetic background including a chromosomal translocation, t(12;22)(q13;q12), or a resultant EWSR1-ATF1 fusion gene.
Clear cell sarcoma (CCS) of tendons and aponeuroses/malignant melanoma (MM) of soft parts is a rare tumor and in the majority of cases presents a characteristic reciprocal translocation t(12;22)(q13;q12) that results in fusion of the EWS and ATF1 genes.
Although some investigators argue that CMCT is a variant of CCS, we think it should be separated from CCS, and subcutaneous/dermal CCS should be confined to tumors with EWSR1-ATF1/ CREB1 fusion.
In the new review all the tumors were re-classified as, ES (n=16), Ewing-like tumor with EWSR1 rearrangement and amplification and possible EWSR1-NFATC2 gene fusion (n=1), CIC-rearranged sarcomas or undifferentiated sarcoma, most consistent with CIC-rearranged sarcoma (n=7), sarcoma with BCOR-alteration or undifferentiated sarcoma, consistent with BCOR-associated sarcoma (n=3), neuroblastoma (n=2), unclassifiable neoplasm with neuroblastic differentiation (n=1), malignant rhabdoid tumor (n=2), lymphoblastic lymphoma (n=1), clear cell sarcoma of the gastrointestinal tract (n=1), small cell carcinoma (n=1), sclerosing rhabdomyosarcoma (n=1), desmoplastic small round cell tumor (n=1), malignant peripheral sheath nerve tumor (n=1), poorly-differentiated synovial sarcoma (n=1), Possible gastrointestinal stromal tumor/GIST with predominant round cells (n=1) and possible SMARCA4-deficient-sarcoma (n=1).
Activation of the EWSR1-ATF1 oncogene is probably an early step in the transformation process, but the overall gene expression patterns are likely to vary considerably between AFH and CCS, in keeping with their clinicopathologic differences.