CD274 and post-transplant lymphoproliferative disease: A duodenal biopsy 3 months later revealed FFH PTLD with just 5% PD‐L1‐positive macrophages (Figure 3K), and, of note, PD‐L1 negativity of the B‐cell blasts, which were PD‐L1‐positive in a sample of the rectum (p‐PTLD) (Figure 3H,I) taken simultaneously to the duodenal biopsy.