Expression of CXCL13 by neoplastic cells in angioimmunoblastic T-cell lymphoma (AITL): a new diagnostic marker providing evidence that AITL derives from follicular helper T cells.

Angioimmunoblastic T-cell lymphoma (AITL) represents a distinct entity among peripheral T-cell lymphomas (PTCLs). The cellular origin of AITL remains unknown, although a possible derivation from follicular helper T cells (TFH) has been suggested based on the CD4/Bcl-6 phenotype. It has been recently shown that expression of CXCL13, a chemokine critically involved in B-cell migration into germinal centers, is characteristic of TFH cells, as compared with other T helper subsets. We compared CXCL13 expression in 29 AITLs, 20 PTCLs, unspecified, 10 anaplastic large cell lymphomas (ALCL), and 4 other PTCLs. We showed that CXCL13 is expressed by AITL (29 of 29, 100%) and a subset of PTCL, unspecified (6 of 20, 30%), which all showed borderline features with AITL, but in only 1 of 10 (10%) ALCLs, and 0 of 4 other PTCLs. Two-color immunostainings further showed that CXCL13 was found in the cytoplasm of atypical CD5-positive T cells that expressed CD10. We conclude that CXCL13 expression is a common characteristic of AITL, which can help to delineate the morphologic spectrum of the disease, and further supports its derivation from TFH cells. CXCL13 expression may also provide an additional useful tool for the diagnosis of AITL.