For example, 19DD, a HIST + DD sample, harbored an 8.1-fold copy-number amplification in the chr4 region, including TDO2, which encodes a tryptophan 2,3-dioxygenase that converts tryptophan to kynurenine, a metabolite known to be involved in tumor growth and poor prognosis. Here, TDO2 is linked to neoplasm.