EWSR1-NFATC2 and FUS-NFATC2 Gene Fusion-Associated Mesenchymal Tumors: Clinicopathologic Correlation and Literature Review

Figure 2

Imaging of a painful lesion of the proximal diaphysis of the left tibia in a 42-year-old man ((a, b) CT, (c) 3D CT reconstruction, and (d) MRI) showed a cortex-based mass with intraosseous and extraosseous extension. (e) Direct smear of the biopsy (Papanikolaou stain, 400x) showed a small, blue, round cell population. (f) Histological examination revealed tumor cells with clear cytoplasm, embedded in collagen-rich extracellular matrix (H&E; 200x). The cells have a low proliferation rate ((g) MIB1 immunohistochemistry; 100x) and focal cytokeratin (AE1/AE3) ((h) 200x) and CD99 expression ((i) 400). (j) On break-apart probe FISH analysis of the EWSR1 gene, one to two fused signals (white arrows) and low-grade amplified red signals (red arrows) in the tumor cell nuclei were seen, suggesting rearrangement of the EWSR1 gene with additional chromosomal aberrations.