RESUMO
We present the case of a young lady who had been treated for acute myelocytic leukemia at the age of 14 by means of allogeneic bone marrow transplantation, the donor being her sister. At the age of 28 she underwent modified radical mastectomy for invasive breast adenocarcinoma. Genetic analysis revealed chimeric cellular populations on both the tumour and normal tissues of the patient with preponderance of donor-derived cells. We conclude that the patient's epithelia had been repopulated by donor-derived hemopoietic stem cells which gave rise to a malignant mammary neoplasm several years later. The donor remains healthy to date. This case adds weight to the theory of pluripotent normal and neoplastic stem cell histogenesis and emphasizes the pivotal role of supporting host stroma in carcinogenesis.