ICOS and angioimmunoblastic T-cell lymphoma: The tumor cells were CD8+, and despite ICOS, BCL-6, and partial PD1 expression, this conflicted with the proposed COO of TFHL and, thus, is considered not diagnostic of AITL, Additionally, the constellation of mutations in this case (STAT3, NOTCH2, VAV1, TBL1XR1, and CSF3R) is not typical for TFHL (Supplemental Table 2) and a diagnosis of PTCL, NOS with features of AITL was favored.