Several reports on transmitted malignancies have relied partially or totally on the investigation of kariotype mismatch between the tumour with respect to recipient tissues for assessing imputability. This strategy is generally limited to those cases where a gender mismatch exists between the donor and the recipient. The interphase Fluorescence In Situ Hybridization (FISH) for sex chromosomes has been used in these situations. As such, there would be no problem even with a neoplastic karyotype, since the sex chromosomes are still identifiable, so they would not lose these particular chromosomes (X and Y). Such studies are possible on routinely processed, formalin fixed paraffin-embedded tissue samples.