CD5 and T-cell and NK-cell neoplasm: Flow cytometry of peripheral blood identified an aberrant CD8+ T‐cell subset lacking CD5 (6.6% of events) with polyclonal T-cell receptor (TCR) β/γ rearrangements. In the context of acute EBV-associated hyperinflammation, loss of CD5 on a minority CD8+ subset is compatible with reactive cytotoxic T-cell activation and is not, by itself, diagnostic of a T-cell neoplasm; interpretation should rest on the total clinicopathologic picture.