Co‐occurrence of Epstein–Barr virus‐positive nodal T/NK‐cell lymphoma and nodal T‐follicular helper cell lymphoma of different clonal origins: An autopsy case report

Nodal T‐follicular helper cell lymphoma (TFHL) is a subset of T‐cell lymphoma and frequently co‐occurs with Epstein–Barr virus (EBV)‐positive B‐cell lymphoma but not with T/NK‐cell lymphoma. Recently, a new entity with a worse prognosis, called EBV‐positive nodal T/NK‐cell lymphoma (NTNKL) has been established. Here, we report an autopsy case of synchronous multiple lymphomas, including TFHL and NTNKL. The patient was a 78‐year‐old female admitted with pneumonia. Although pneumonic symptoms were improved, fever, pancytopenia, and disseminated intravascular coagulation emerged, implicating lymphoma. She died on the 21st hospital day without a definitive diagnosis. The autopsy revealed the enlargement of multiple lymph nodes throughout her body. Histological analysis revealed three distinct regions in the left inguinal lymph node. The first region consists of small‐sized lymphocytes with T‐follicular helper phenotype and extended follicular dendritic cell meshwork, indicating TFHL. The second region included EBV‐positive large B cells. The third region comprised EBV‐positive large cells with cytotoxic T/NK cell phenotype, indicating NTNKL. Clonality analysis of the first and the third regions showed different patterns. Since various hematopoietic malignancies progress from common clonal hematopoiesis according to existing literature, this case may help to understand TFHL and NTNKL.