This is a observational, retrospective (a study in which the participants are identified and then followed backward in time, for the outcome of the study) study. In this study review of all reports of possible cases of hepatosplenic T-cell lymphoma (HSTCL) that were identified within the PALGA database of pathology results for The Netherlands from 1995 to 2008. All patients whose information is contained within the PALGA database were prescribed treatments by a physician on the basis of usual clinical practice or may have received other treatments, including experimental drugs, while participating in an interventional clinical study. The identified data on each of the patients with reports of HSTCL will be collected from the pathologist(s) who prepared the report and from the physician(s) who treated the patient at the time of diagnosis.