Strong expression of chemokine receptor CCR9 in diffuse large B-cell lymphoma and follicular lymphoma strongly correlates with gastrointestinal involvement

Summary The gastrointestinal (GI) tract is the most common site of extranodal B-cell lymphomas. However, it is unclear how neoplastic lymphoid cells preferentially home there. We hypothesize that expression of the GI-homing chemokine receptor CCR9 may account for the dissemination of B-cell lymphomas to the GI tract. To test our hypothesis, we compared the expression of CCR9 using immunohistochemistry on GI versus nodal diffuse large B-cell lymphoma and follicular lymphoma. We found that 27 (66%) of 41, 12 (29%) of 41, and 2 (5%) of 41 of GI lymphoma cases demonstrated 3+, 2+, and 1+ CCR9 staining, respectively. In contrast, 2 (5%) of 39, 5 (13%) of 39, 8 (20.5%) of 39, and 24 (61.5%) of 39 nodal-restricted lymphoma cases demonstrated 3+, 2+, 1+, and 0+ CCR9 staining ( P P P P