Overlap at the molecular and immunohistochemical levels between angioimmunoblastic T-cell lymphoma and a subgroup of peripheral T-cell lymphomas without specific morphological features.

The overlap of morphology and immunophenotype between angioimmunoblastic T-cell lymphoma (AITL) and other nodal peripheral T-cell lymphomas (n-PTCLs) is a matter of current interest whose clinical relevance and pathogenic background have not been fully established. We studied a series of 98 n-PTCL samples (comprising 57 AITL and 41 PTCL-NOS) with five T antibodies (CD10, BCL-6, PD-1, CXCL13, ICOS), looked for mutations in five of the genes most frequently mutated in AITL (, and ) using the Next-Generation-Sequencing Ion Torrent platform, and measured the correlations of these characteristics with morphology and clinical features. The percentage of mutations in the and genes was similar (23.5% of cases). was mutated in 14.3%, in 11.2% and in 7.1% of cases, respectively. In the complete series, mutations in gene were associated with the presence of mutations in and ( 0.001, 0.043, and 0.029, respectively). Fourteen cases featured mutations without mutations. A close relationship was found between the presence of these mutations and a T-phenotype in AITL and PTCL-NOS patients. Interestingly, BCL-6 expression was the only T marker differentially expressed between AITL and PTCL-NOS cases. There were many fewer mutated cases than there were cases with a T phenotype. Overall, these data suggest alternative ways by which neoplastic T-cells overexpress these proteins. On the other hand, no clinical or survival differences were found between any of the recognized subgroups of patients with respect to their immunohistochemistry or mutational profile.