CCR9 and plasma cell myeloma: The expression mRNA levels for CCR9 in other leukemias, lymphomas or myelomas is much lower, although about 30% of the tumor samples in Splenic marginal zone lymphoma and about 20% of the samples in Hairy cell leukemia, Mantle cell lymphoma or Hodgkin lymphoma express high levels of CCR9 mRNA (see Figure 1A).