RECQL4 and osteosarcoma: Out of these pathogenic variants, two (c.[1568G>C;1573delT]; c.1878+32_1878+55del) directly impact and one (c.1048_1049del) leads to the lack of the helicase domain confirming the known assumption that patients with at least one RECQL4 truncating mutation disrupting the helicase domain have an increased risk to develop osteosarcoma at young age (mean age 11 y) [2].