Secondary neuroendocrine tumor after allogeneic bone marrow transplantation.

Here we report a case of aggressive neuroendocrine tumor (NET), which is an extremely rare secondary solid tumor that occurs after allogeneic hematopoietic cell transplantation (allo-HSCT). A patient with chronic active Epstein-Barr virus infection received allo-HSCT from an HLA-DR two allele-mismatched unrelated donor. Four years later, he developed NET with multiple metastases. He received thoraco-abdominal irradiation as a conditioning regimen, and developed repeated episodes of intestinal graft-versus-host disease, for which he received long-term immunosuppressive therapy. Although these factors may be potential contributing factors to the development of secondary NET, the exact pathogenesis remains unclear.