Bone marrow. (A) Aspirate smears show many dysplastic erythroid precursors with bizarre nuclear configurations (arrows) as well as (B) rare tumor giant cells (Wright Giemsa, original magnification ×1000). (C) Ill-defined tumor nodules efface the bone marrow architecture within the core biopsy (hematoxylin and eosin, ×100). (D) The tumor nodules contain many irregular mononuclear cells as well as scattered bizarre multinucleated tumor giant cells with hyperchromatic nuclei with coarse chromatin and macronucleoli (hematoxylin and eosin, ×400). (E) Occasional binucleated Reed-Sternberg like tumor cells are present (hematoxylin and eosin, ×1000). Immunohistochemical studies performed on the bone marrow core biopsy are consistent with classical Hodgkin lymphoma. (F) The tumor cells are strongly positive for CD30 expression with membranous and Golgi positivity (×400). (G) Within the bone marrow core biopsy, there is a conspicuous background histiocytosis with prominent hemophagocytosis (hematoxylin and eosin, ×400). Arrows indicate phagocytosed erythroid precursors (e) as well as an ingested band form (b). (H) An immunohistochemical stain for CD68 highlights abundant background histiocytes, many of which contain hematopoietic elements (×400).