TCF21 and clear cell sarcoma of kidney: Our study as part of the NCI‐initiated therapeutically applicable research to generate effective treatment project (TARGET) identified hypermethylation of the 5′ region of transcription factor 21 (TCF21) in all studied CCSK samples, except for samples harboring the YWHAE‐NUTM2 fusion transcript (Gooskens et al., 2015).