Figure 1.

Secondary break-apart EWSR1 patterns in SMARCB1-deleted tumors. A: SMARCB1 and EWSR1 genomic positions on chromosome 22 ideogram, with correspondent fluorochrome-labeled DNA probes used in the 3-color FISH assays (red: intragenic SMARCB1, yellow: centromeric EWSR1, green: telomeric EWSR1). B: Poorly differentiated chordoma showing compact sheets of epithelioid cells with moderate nuclear pleomorphism (Case 1, 400x) and (C) strong T-brachyury nuclear immunoreactivity (400x). D: The 3-color FISH assay showed homozygous SMARCB1 deletion (loss of both red signals) and EWSR1 break-apart pattern (yellow and green split signals with lower intensities). E: Extrarenal rhabdoid tumor resembling Ewing sarcoma, characterized by solid sheets of small round cells with prominent nucleoli (Case 2, 400x) and (F) loss of SMARCB1 expression (internal positive control, inflammatory and endothelial cells; 400x). G: The 3-color FISH revealed a homozygous SMARCB1 deletion (loss of both red signals) and coexistent EWSR1 regional abnormalities (the arrow): one intact yellow signal (telomeric EWSR1 deletion) and one split pair of smaller-sized yellow and green signals (EWSR1 regional break and deletion). [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]