Over the last several decades, survival rates for childhood cancer have steadily increased. Spermatogonial stem cells are responsible for the continual production of spermatozoa throughout adult life. Autotransplantation is considered more acceptable than allotransplantation or xenotransplantation, although both of the latter have been used successfully in mouse models. Spermatogenesis in vitro from biopsied germ cells is considered to be an excellent alternative for pre-pubertal boys with malignancies, particularly of hematopoietic origin, who carry a risk of relapse after transplantation. Despite significant advances in spermatogonial cell biology and subsequent fertility management, malignant contamination remains one of the main concerns surrounding autologous transplantation. The potential for transferring tumor cells within cryopreserved and subsequently cultured and/or expanded testicular tissue back into the patient is of paramount concern. Children most at risk of transmitting cancer cells include those with a haematological malignancy such as acute leukemia.