Tissue Preservation and FFPE Samples: Optimized Nucleic Acids Isolation in Ewing Sarcoma.

Different methods have been described for the preservation of biopsy or resection samples. In routine pathology, the cheapest and most used method is fixation of samples in formalin and embedding in paraffin (FFPE samples). This method preserves tissue samples for a very long time and is suitable for several specialized techniques, such as fluorescence in situ hybridization (FISH) and immunohistochemistry, the latter being the most frequent and often the only additional method used for the establishment of the final diagnosis. However, in light of the growing need for next-generation sequencing and microarray technologies that are often very helpful to establish and/or confirm diagnoses in the field of pediatric sarcoma (including Ewing sarcoma), preservation of high-quality and quantity of nucleic acids (DNA/RNA) is desirable. Herein, we describe how to ideally preserve samples, as well as how to proceed to isolate nucleic acids for successful subsequent molecular assays with a special focus on Ewing sarcoma samples.