Wong MK, et al. – Experts aspired to characterize 11 histologically diagnosed clear cell sarcoma of kidney (CCSK) immunohistochemically (with cyclin D1 (CCND1), BCOR and CCNB3 stains), and genetically. The majority of the CCSKs in the cohort displayed BCOR internal tandem duplications (ITD), and none had the YWHAE–NUTM2 gene fusion. Findings verified the strong, diffuse cyclin D1 (CCND1) immunoreactivity in CCSKs described in recent reports. In all CCSKs with BCOR ITD, BCOR immunoreactivity was not consistently positive. Therefore, it could not be used as a diagnostic immunohistochemical stain to identify BCOR ITD cases.