Conclusion: MicroRNAs are differentially expressed between astrocytomas and NB. The low expression of miR-128 and -221 could be a potential marker in recurrent pediatric astrocytomas, and both are associated to less survival. Embedded tissue is useful to describe and evaluate expression of molecular markers of malignancy. Objective: Isolation of genomic DNA from formalin fixed paraffin embedded (FFPE) tissues is a critical step for molecular diagnostic assays. Horizon Diagnostics has generated FFPE cell line reference standards containing defined mutant allelic frequencies, enabling the quality control of both assay sensitivity and DNA extraction.