Immunohistochemistry of a pretreatment lymph node biopsy sample from a patient with complete response to varlilumab. (A) Hematoxylin and eosin stain (magnification ×20) from a patient with classical Hodgkin lymphoma. (B) Atypical lymphohistiocytic infiltrate within a background of normal reactive cells (magnification ×100). (C) CD27 expression on malignant cells, intratumoral lymphocytes, and histiocytes. Malignant cells and intratumoral T cells were positive for CD27 expression (magnification ×100). (D) CD70 staining was negative on both malignant cells and the intratumoral immune infiltrate (magnification ×100).