Combination of multicolor flow cytometry for circulating lymphoma cells and tests for the RHOAG17V and IDH2R172 hot-spot mutations in plasma cell-free DNA as liquid biopsy for the diagnosis of angioimmunoblastic T-cell lymphoma.

We applied two-step multicolor flow cytometry (FCM) for circulating lymphoma cells in the blood of 20 patients with angioimmunoblastic T-cell lymphoma (AITL) and confirmed neoplastic T-cells in all. Eleven exhibited dim expression of CD3 and 7 lost its expression. The proportion of CD10+ lymphoma cells ranged widely from 0 to 100%, with a median of 15.7%. Ten patients demonstrated expansion of a single T-cell receptor β-chain repertoire. Lymphoma cells comprised 0.01 to 18.22% (median, 0.26%) of white cells and the absolute numbers ranged from 0.5 to 1491.6 cells (median, 29.3 cells) per microliter of blood. We next found that 14 (70%) and 3 (15%) patients carried RHOAG17V and IDH2R172 mutations, respectively, in cell-free DNA (cfDNA) in the plasma. The combination of multicolor FCM of the blood, and tests for RHOAG17V and IDH2R172 hot-spot mutations in plasma cfDNA provides a blood-based 'liquid biopsy' for the diagnosis of AITL.