Bone marrow aspirate containing hemophagocytosis figures, one of them morphologically resembling a signet-ring cell, in a patient who underwent CART cell therapy for Diffuse Large B-Cell Lymphoma, presenting with Grade 2 Cytokine Release Syndrome treated with tocilizumab; splenomegaly; hypofibrinogenemia; hypertriglyceridemia; and elevated liver enzymes. Though hemophagocytic lymphohistiocytosis (HLH)-like toxicities after CART cell therapy have been widely reported [1], the ocurrence of signet-ring histiocytes in hemophagocytosis is typically associated with typhoid fever [2] and, to our knowledge, has not previously been described following CART cell therapy.

1. Hines MR et al. Immune Effector Cell-Associated Hemophagocytic Lymphohistiocytosis-Like Syndrome. Transplant Cell Ther. 2023 Jul;29(7):438.e1-438.e16. doi: 10.1016/j.jtct.2023.03.006.

2. Jianfeng Zhu, Wei Guo; Signet-ring histiocytes in typhoid fever. Blood 2017; 130 (23): 2574. doi: https://doi.org/10.1182/blood-2017-09-805614