Metastatic neuroblastoma in fertility preservation biopsy of clinically normal testis: a case report.

RESEARCH QUESTION: Is there potential for the detection of neuroblastoma malignancy in testicular tissue extracted for fertility preservation for prepubertal boys at the time of tissue freezing? DESIGN: This is a case report. RESULTS: A boy was diagnosed with primary localized left adrenal neuroblastoma, with complete resection of the tumour. During 6 months' surveillance, he developed a relapse in the left para-renal region with progression of molecular and chromosomal features into undifferentiated neuroblastoma. Before highly gonadotoxic treatment, testicular biopsy for fertility preservation was taken, from a clinically normal testis. Histopathological examination of the testicular biopsy revealed metastatic neuroblastoma. CONCLUSIONS: Metastatic neuroblastoma detected histologically in a clinically normal testis highlights the importance of routine histological examination at the time of testicular cryopreservation. The histological evaluation of gonadal tissue for potential malignant contamination before freezing should be mandatory, regardless of the malignancy diagnosis. Advances in sensitive molecular detection and in-vitro maturation are critically required to decrease future risk of disease recurrence in both solid and haematological malignancies.

Chapter 9 Slow Freezing and Thawing of Human Cleavage Stage Embryos.

The ability to store human embryos in a viable state at very low temperatures has been critical to the evolution of responsible practice in clinical Assisted Reproductive Technology (ART). It has encouraged a reduction in the frequency of simultaneous multiple embryo transfer and thereby reduced the risks associated with multiple pregnancy while maintaining high cumulative pregnancy rates from single oocyte collection cycles. In this chapter, we describe a simple slow freezing procedure for human early cleavage stage embryos that results in a high proportion of post-thaw embryos surviving and retaining their implantation potential.

Embryonic factors affecting outcome from single cryopreserved embryo transfer.

Multiple pregnancy minimization by single embryo transfer is becoming more prevalent, but is less common in the case of cryopreserved embryos. This study defines embryonic characteristics in single cryopreserved embryo transfers associated with success rates equivalent to those achieved when transferring two cryopreserved embryos. In a retrospective analysis of 6916 cryopreserved day-2 embryo transfer procedures, transfer of two cryopreserved embryos resulted in higher clinical pregnancy rates when compared with transfer of a single thawed embryo but was also associated with elevated multiple pregnancy rates (26.7% in women under 36). Optimal outcome (implantation rate of 30.9%) from single cryopreserved embryo transfer (SCET) in women under 36 was associated with cryopreservation at the 4-cell stage, loss of fewer than two blastomeres and subsequent cleavage of at least two surviving blastomeres. In comparison, transfer of two cryopreserved embryos in women under 36 resulted in pregnancy and implantation rates of 25.5 and 16.1% respectively. Interestingly, in cryopreserved 4-cell stage embryos, loss of a single blastomere did not reduce implantation potential and cleavage of only a single post-thaw blastomere was not indicative of increased implantation potential. Establishment of these critical thresholds provides a rational basis for SCET.

The application and impact of cryopreservation of early cleavage stage embryos in assisted reproduction.

The contribution of cryopreserved embryos to the overall outcomes achieved by a clinical assisted reproduction programme has increased in importance with the trend towards reducing the numbers of fresh embryos transferred following in vitro fertilisation. Although cryopreservation appears to fully preserve developmental potential in early cleavage stage embryos that survive intact, it results in a reduction in potential when blastomere loss occurs during freezing and thawing. Overall, it can be estimated that cryopreservation results in approximately a 30% reduction in the potential for pregnancy in a population of embryos. Both blastomere survival and post-thaw resumption of mitosis can act as markers of implantation potential in frozen/thawed embryos. Application of strict criteria for freezing embryos and transferring thawed embryos may enhance apparent success rates, but may also result in some pregnancy potential being discarded. The role of embryo cryopreservation in minimising the incidence of multiple pregnancy must be balanced with the need for efficiency in the quest to establish pregnancy.

Blastocyst formation and cell numbers in human frozen-thawed embryos following extended culture.

BACKGROUND: Blastomere loss following human embryo cryopreservation has been shown to be associated with reduced implantation potential. In order to elucidate the underlying mechanism, the present study was designed to investigate the consequences of blastomere loss on subsequent preimplantation development in vitro. METHODS: Cryopreserved embryos destined for disposal were thawed and cultured for 96 h prior to determination of total cell numbers in resultant blastocysts. RESULTS: The proportion of embryos which formed blastocysts in vitro was significantly reduced when blastomere loss was evident in thawed embryos (25 versus 41% in fully intact thawed embryos). In addition, blastocysts from partially intact thawed embryos exhibited a significant reduction in total cell number (45.0 versus 58.4 in blastocysts from fully intact thawed embryos). Development to the blastocyst stage was significantly less frequent in fully intact thawed embryos which had been generated using ICSI (19%) compared with standard IVF (47%), although cell numbers in the resultant blastocysts were similar (57.1 and 58.6 respectively). CONCLUSIONS: Blastomere loss following cryopreservation impairs preimplantation development and results in reduced cell numbers at peri-implantation stages. ICSI is associated with reduced potential for post-thaw development of cryopreserved embryos in vitro.