Evidence of donor-derived hematologic malignancies after hematopoietic stem cell transplantation.

Increasing the upper age limit for recipients of hematopoietic stem cell transplantation (HCT) naturally has also increased the age of the corresponding related donor population. Because aging is a risk factor for malignancies, the risk of transferring preexisting malignant or premalignant hemopoietic clones in the process of HCT might be expected to increase as well. Anecdotal clinical cases of malignancies derived from donor cells in patients undergoing HCT have been published since 1971. In this article, we report 12 new cases that fit 2 different categories: (1) cases in which clones with characteristics of lymphohemopoietic malignancies were transferred from the donors to the recipients and (2) cases in which the malignant clone evolved from healthy donor cells once transplanted into the recipient. Donors in the first group were significantly older than donors in the second group. A more systematic examination of the prevalence and biology of donor malignancies would merit study.