STR typing from punched FFPE tissues: resolving suspected contamination and fetal-maternal mixture in two cases.
Barbara Di Stefano, Rossana Bussani, Solange Sorçaburu Ciglieri et al.
✦ AI-curated · Sources linked
Case in brief
Two casework applications used targeted punches from formalin-fixed, paraffin-embedded tissue followed by STR profiling. In one, a focus of high-grade urothelial carcinoma in a prostate surgical specimen prompted concern about cross-sample contamination. Profiles from carcinoma and benign prostate punches were fully concordant (LR = 2.5 × 10²¹), supporting a common donor and excluding inadvertent tissue transfer. In the other, morphologically guided sampling isolated chorionic villi from heterogeneous aborted embryonic material for paternity assessment. Despite low-level maternal DNA, mixture interpretation reconstructed a complete embryonic genotype and yielded conclusive paternity (LR = 2.2 × 10¹⁰).
What made this case unusual
The two distinct interpretive challenges—suspected tissue transfer in a surgical specimen and fetal-maternal DNA mixture in heterogeneous embryonic material—were addressed using targeted FFPE punches and STR profiling.
Diagnostic / clinical pearl
Morphology-guided punching can target the tissue of interest in heterogeneous FFPE material; STR mixture interpretation may still recover a complete embryonic genotype when low-level maternal DNA is present.
Why it matters
The cases illustrate a practical approach to assessing suspected contamination and recovering targeted genotypes from complex tissue specimens.