Kussick et al. reported two cases of mature T cell lymphoproliferative disorder with cells exhibiting a CD3+, CD4+ phenotype, without clinical or morphological features suggesting either T-PLL (absence of the prolymphocytoid morphology, and of associated hepatosplenomegaly and/or generalized lymphadenopathy), or MF/SS, ATLL, T-LGLL or an underlying peripheral T cell lymphoma. The gene discussed is CD4; the disease is adult T-cell leukemia/lymphoma.