Figure 5.

The broad spectrum of EwS and related entities in diagnostical work-up. Representative images of small round cell sarcomas showing classic EwS with uniform small round cells, strong expression of CD99, and aberrant patterns of EWSR1 break-apart FISH, pointing to a genomic rearrangement (upper panel left). EWSR1-NFATc2 translocated sarcoma with a more epithelioid cytology, positivity for CD99, and amplified isolated red signals in EWSR1 break-apart FISH, suggesting rearrangement of the EWSR1 gene associated with additional chromosomal aberrations (upper panel right). BCOR-CCNB3 translocated sarcoma with primitive round to spindle cells arranged in sheets, heterogeneous CD99 expression, and positivity for BCOR by immunohistochemistry (lower panel left). CIC-rearranged sarcoma with a higher degree of cytological variability compared to classic EwS, inconsistent patchy CD99 positivity, and a classic break-apart in a CIC FISH assay (lower panel right).