Primary Low-Grade Fibromyxoid Sarcoma of the Kidney in a Child with the Alternative EWSR1-CREB3L1 Gene Fusion

We present the case of a 6-year-old boy with a deceptively bland spindle cell renal neoplasm found to harbor the EWSR1-CREB3L1 gene fusion. This fusion has recently been described as a variant translocation in low-grade fibromyxoid sarcoma (LGFMS), a tumor more typically characterized by a recurrent t(7;16) chromosomal translocation, resulting in the fusion of FUS and CREB3L2 genes. LGFMS is an indolent tumor with late metastatic potential and a propensity for long-term disease recurrence. The tumor is rare in children, with only 33 published cases. In the pediatric population, it has not previously been reported arising in the kidney.