PDCD1 and Hodgkins lymphoma: 23 demonstrated that, in classical Hodgkin lymphoma patients, PD‐1 expression on lymphocyte predominant pathologic tissues was positive, and there was significant difference in prognosis between PD‐1‐positive cells >23/mm2 (29 deaths/75 patients) and PD‐1‐positive cells <23/mm2 (9 deaths/23 patients) (P = 0.005).