Repeated relapses of acute myelogenous leukemia in the isolated extramedullary sites following allogeneic bone marrow transplantations

Isolated extramedullary (EM) relapses of acute myelogenous leukemia (AML) after allogeneic hematopoietic stem cell transplantation (allo-HSCT) have been reported to be rare, and are usually followed by bone marrow relapses. We report a 49-year-old man with AML with the unfavorable chromosome abnormality 7q-, who was treated by allo-HSCT. Fifteen months after allo-HSCT, the patient initially developed a relapse only in his inguinal lymph nodes, and then bone marrow relapse became evident one month after the EM relapse. Subsequently, the patient received chemotherapy and a second allo-HSCT from another donor, but he suffered another relapse in different EM sites including the skin and central nervous system with a persistently normal marrow. This case is characterized by repeated relapses in isolated EM sites after allo-HSCT and suggests that the anti-leukemic effects of chemotherapy and/or graft-versus-leukemia effects in the EM sites might not be so uniformly effective as that in the marrow. Accordingly, we should be aware that AML relapses can occur repeatedly only in isolated EM sites post allo-HSCT, resulting in treatment failure and a poor prognosis.