Flowchart of all individuals studied from 1997 to 2018. ∗Histiocytosis-related disease = ICD-10 codes D76.0 to D76.3 and C96.0, and cancer diagnosis = ICD-10 codes C00.0 to C97.00. ∗∗The Langerhans cell histiocytosis = ICD-10 codes D76.0, C96.0, C96.5, C96.6, and the other specified histiocytic syndromes = ICD-10 codes D76.3A to E. ∗∗∗Probable malignancy-associated HLH (mal-HLH) is defined as HLH within −90 to +365 days in relation to the cancer diagnosis.