[Extramedullary relapse of acute lymphoblastic leukemia in the breast after unrelated allogeneic bone marrow transplantation].

A 28-year-old female presented with an isolated extramedullary relapse in the breast following an unrelated allogeneic bone marrow transplantation(UBMT)for acute lymphoblastic leukemia. She complained of a tumor in her right breast with hematological complete remission 23 months after her first UBMT. The extramedullary lesion resolved with chemotherapy, and she then received a second UBMT. Although there had been no relapse of leukemia in the bone marrow and extramedullary sites, she died from a herpes simplex virus infection in the central nervous system. Extramedullary relapses in the so-called 'sanctuary'sites after hematopoietic stem cell transplantation are unusual, and breast recurrences are even more rare. A treatment strategy for unusual sites of relapse after BMT should be established.