IL21 and neoplasm: Further, we traced the transitional relationship of Tex cells in the two tumor sites based on TCR information and STARTRAC, a tool of clonotype tracking to define clonal expansion, migration, and developmental transition of T cells.[17] STARTRAC analyses revealed transitional processes of the mLN‐enriched cells (CD4‐c02‐Itgb1 and CD4‐c03‐Il21) with other clusters in tumors.