EWSR1-SMAD3-rearranged fibroblastic tumor: a case report with literature review.

This paper discusses an EWSR1-SMAD3-rearranged fibroblastic tumor (ESFT) occurring in the wrist of a 5-year-old child and summarizes its clinicopathological features, immunohistochemical phenotype, and molecular characteristics to improve the accuracy of clinical diagnosis. A retrospective analysis was performed on the clinical manifestations, histopathology, immunohistochemical phenotype, and molecular characteristics of a 5-year-old patient with recurrent ESFT. Additionally, this paper presents a literature review of relevant studies on ESFT. Among the 21 cases of ESFT, including the present case, the disease primarily affects young and middle-aged adult females, with most tumors measuring 1-2 cm in diameter. It preferentially occurs in the soft tissues of the distal extremities-particularly the foot-and exhibits low-grade invasiveness. Histomorphologically, the tumor is composed of uniform spindle-shaped fibroblasts arranged in fascicular and interlacing patterns, with no prominent nucleoli or mitotic figures. A zonation pattern, focal microcalcification, and interstitial myxoid change are observed in some cases. Immunohistochemistry reveals diffuse, strong ERG expression in tumor cells; FISH molecular detection shows EWSR1 break-apart; and NGS results confirm EWSR1-SMAD3 rearrangement. ESFT is a benign neoplasm with a risk of local recurrence. It exhibits complex histomorphological features but demonstrates diffuse, strong immunoreactivity for ERG on immunohistochemistry and harbors characteristic genetic alterations.