ATRX and undifferentiated pleomorphic sarcoma: The contrast with other types of sarcomas is illustrated by a study of ALT phenotype and ATRX status in 519 sarcoma samples which found loss of ATRX expression in approximately 50% of ALT‐positive leiomyosarcomas, undifferentiated pleomorphic sarcomas, and pleomorphic liposarcomas, whereas ATRX mutation and loss of expression was observed in only 30% of osteosarcomas (Liau et al, 2015).