Morphologic features of different cases of HSTCL. (A) Spleen involvement with sheets of small neoplastic lymphoid cells involving cords and sinuses of spleen (hematoxylin and eosin [H&E] stain; original magnification ×600). (B) Bone marrow aspirate in a patient with progressive HSTCL (Wright-Giemsa stain; original magnification ×1000). The neoplastic T cells in this case (highlighted with thin tall arrows) are medium sized and demonstrate fine chromatic, resembling blasts. A rare neoplastic cell is demonstrating hemophagocytosis (highlighted with a thick short arrow). (C) Bone marrow core biopsy showing sinusoidal expansion by medium-sized lymphoid cells (H&E stain; original magnification ×600). (D) CD3 immunohistochemical stain in bone marrow core biopsy, highlighting the sinusoidal expansion by neoplastic T cells (original magnification ×1000).