BM features of LGL leukemia. (A) Hematoxylin and eosin staining (HES) of marrow biopsy reveals a slightly hypercellular marrow with a subtle increase in interstitial lymphocytes. (B) CD3 staining reveals the LGL interstitial infiltration. (C) Immunoperoxydase staining for CD8 demonstrates clusters of at least 8 cytotoxic lymphocytes CD8⁺. (D) Linear array of intravascular LGL demonstrated by Granzyme B (GzB) staining. (E) CD57 staining reveals the LGL interstitial infiltration. Original magnifications ×4 (A), ×40 (B), ×20 (C), ×100 (D), and ×20 (E). Images courtesy of Philippe Gaulard (Department of Pathology, Henri Mondor Hospital, Assistance Publique–Hôpitaux de Paris, Creteil, France) and Patrick Tas (Department of Pathology, Rennes University Hospital, Rennes, France).