In clinical practice, the detection of HAVCR2 mutations in children and adolescents with SPTCL with or without HLH/HLH-like systemic illnesses, and in patients with idiopathic HLH/HLH-like systemic illnesses, should be helpful in guiding treatment selection and predicting the natural history of the disease. Here, HAVCR2 is linked to subcutaneous panniculitis-like T-cell lymphoma.