ATRX and cancer: The marked difference in ALT activity between ULM and ULMS may serve not only as a diagnostic marker to distinguish benign from malignant tumors, but also as a prognostic factor in ULMS and a potential therapeutic vulnerability, as ATRX-deficient cells exhibit heightened sensitivity to replication stress and DNA damage—features that can be targeted with agents such as PARP inhibitors, WEE1 inhibitors, and G-quadruplex stabilizers; however, this has not yet been achieved in ULM or ULMS in vivo or in vitro experiments [176,177,178].