ERBB4, an epidermal growth factor, and ZEB2, a zinc finger E-box homeobox binding transcription factor, are well studied in other cancers but less understood in B-cell lymphomas.33,34ERBB4 mutations have been described in the majority of PCNSL cases;35 interestingly, 2 of 4 ECD-PCFCL patients with ERBB4 mutations in our cohort also had CNS involvement. The gene discussed is ERBB4; the disease is cancer.