PDX model of HSTL closely recapitulated features of patient’s disease. (A) Coronal image of computed tomography scan of the chest, abdomen, and pelvis of the patient described in the case scenario. (B) Histopathology images of patient’s bone marrow. Top row, left to right: hematoxylin and eosin (H&E), CD3, CD5; original magnification ×200. Bottom row, left to right: CD2, CD8, and CD4; original magnification ×400. (C) Histopathology images of patient’s liver at the time of autopsy. Images from left to right: H&E, CD3, and CD5; original magnification ×400. (D) Histopathology images of the PDX HSTL model; original magnification ×400 for all images. Top row, left to right: H&E, bone marrow; H&E, liver; H&E, spleen; CD4, spleen. Bottom row, left to right: CD3, spleen; CD5, spleen; CD7, spleen; CD8, spleen. (E) Table showing pathogenic variants detected using targeted panel sequencing in both patient bone marrow and PDX spleen. An asterisk (*) identifies a translation termination codon. VAF, variant allele frequency.