The underlying malignancies in the cohort of 307 adult patients from 1997 to 2018 were 30% B-cell lymphomas, 16% NK/T lymphomas, 6% Hodgkin lymphoma, 16% acute myeloid leukemia (AML), 13% lymphocytic leukemias, 9% other hematologic malignancies, and 11% solid tumors. Survivorship of B-cell lymphomas, Hodgkin lymphoma, and solid tumors was approximately 1.52 times that of NK/T-cell lymphomas, lymphocytic leukemias, and AML at 24 months after HLH diagnosis (range of means 34%-43% versus 19%-26%). Overall survivorship of the entire cohort was 25% (range 20%-30%) at 24 months. The 9 pediatric patients (5 with acute lymphoblastic leukemia; 1 with AML; 2 with B-cell lymphoma; 1 with NK/T lymphoma) had survivorships of 89% (confidence interval [CI] = 43%-98%) at 1 and 2 months and 64% (CI = 24%-87%) at median follow-up 25 months. Professional illustration by Somersault18:24.