TIM‐3 deficiency presenting with two clonally unrelated episodes of mesenteric and subcutaneous panniculitis‐like T‐cell lymphoma and hemophagocytic lymphohistiocytosis

This report offers novel clinical and diagnostic aspects of the association between germline mutations in HAVCR2 and subcutaneous panniculitis‐like T‐cell lymphoma (SPTCL). The patient presented with panniculitis‐like T‐cell lymphoma involving mesenteric fatty tissue associated with hemophagocytic lymphohistiocytosis (HLH). Five years later, he developed a clonally unrelated SPTCL and underwent hematopoietic stem cell transplantation. Retrospectively, he was found to carry germline mutations in HAVCR2 associated with reduced T‐cell immunoglobulin mucin‐3 (TIM‐3) expression. We show that mesenteric fatty tissue localization of SPTCL can be the presenting manifestation of TIM‐3 deficiency, that this condition predisposes to recurrent lymphoma, and that flow cytometry is a possible screening tool.