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

Figure 1

Tumor of the diaphysis of the right femur in a 34-year-old woman. Imaging studies ((a) conventional radiogram, (b) CT, (c) MRI, and (d) PET/CT) revealed a cortex-based mass with intraosseous and extraosseous extension, corresponding to the multilobulated tumor in the cut section of the resection specimen (g). (e) Direct smear of the biopsy (Papanikolaou stain, 400x) showed small, blue, round cell population. (f) On histologic examination, the tumor displayed a prominent collagen-rich extracellular matrix (H&E; 200x) with a moderate proliferation rate ((h) MIB1 immunohistochemistry; 100x) and strong CD99 expression ((i) 400). (j) Break-apart probe FISH analysis of the EWSR1 gene showed one to two fused signals (white arrows) and low-grade amplified red signals (red arrows) in the tumor cell nuclei, suggesting the rearrangement of the EWSR1 gene with additional chromosomal aberrations.