Primary Undifferentiated Sarcoma of the Kidney Harboring a Novel Variant of CIC DUX4 Gene Fusion.
To the Editor: In recent issues of this journal, Yoshida et al1 reported on CIC rearranged sarcomas, and Falzarano et al2 described renal cell carcinomas (RCCs) in patients previously treated for neuroblastoma (NB) Herein, we describe a primary renal CIC DUX4 sarcoma, originally diagnosed as Wilms tumor (WT) in a patient previously treated for contralateral stage 4 NB. CIC DUX4 sarcoma was retrospectively suspected after WT1 nuclear staining was reported in 95% and 70% of CIC rearranged sarcomas.1,3 CIC DUX4 undifferentiated sarcomas are a group of EWSR1negative primitive tumors or Ewinglike sarcomas with fusion of the human homologue of the Drosophila capicua (CIC) gene on chromosome 19 and the double homeobox 4 (DUX4) retrogene on chromosome 4 or 10.1,3 Occasional peripheral tumors harbor variant translocation in which the CIC gene is fused with the forkhead box O4 (FOXO4) gene on the X chromosome.4 Yoshida et al1 reported that the majority of their CIC rearranged sarcomas demonstrated nuclear immunoreactivity for WT1 protein, are positive for calretinin, and negative for NKX2.2. The vast majority of these sarcomas occur primarily in peripheral soft tissues, but visceral cases including the brain are reported.1,5,6
The American journal of surgical pathology