Figure 5

Figure 5

Characterization of ES-like tumors in adult zebrafish. (A) Lateral view of 15-month-old transgenic fish with tumor on dorsal fin. (B) Lateral view of 10-month-old transgenic fish with mass on caudal fin. (C) Lateral view of 12-month-old transgenic fish with mass near anal fin. Black arrows indicate ES-like tumors in (A–C). (D) Magnified image of dorsal fin tumor, dorsal view. (E) Magnified image of caudal fin tumor, lateral view. (F) Magnified image of anal fin tumor, ventral view. (G) Histological analysis of the zebrafish anal fin tumor with H&E staining. (H) PAS staining of the zebrafish anal fin. (I) Histological analysis of the zebrafish anal fin tumor upon CD99 staining, which was performed in two independent fish tumors. These findings indicate that a subset of adult Tg(col2a1a:EWSR1::FLI1:pA) zebrafish develop tumors with histological and immunophenotypic features consistent with ES neoplasms, including small round blue cell morphology on H&E staining, glycogen accumulation detected by PAS staining, and expression of the diagnostic cell-surface marker CD99.