However, MYD88 L265P alone is insufficient for a definitive diagnosis because it is also found in a large percentage of primary CNS lymphoma cases [18,19] and, less frequently, in other low-grade B-cell neoplasms, such as CLL or MZL, which rarely involve the CNS [20,21,22,23,24]. Here, MYD88 is linked to primary central nervous system lymphoma.