Next-generation sequencing (NGS) technology is routinely employed to detect clinically significant variants in the field of precision medicine. Formalin-fixed paraffin-embedded (FFPE) tissues remain a widely used source of genetic material for diagnostic purposes due to their long-term storage stability, which preserves the architecture of tumour tissues. However, the degradation of nucleic acids (NAs) that occurs during the fixation process can lead to unreliable results or hinder analysis. Considering the challenges posed by the quality and quantity of nucleic acids extracted from FFPE samples, the present study aimed to compare paired fresh-frozen (FF) and FFPE samples. The present study also aimed to assess the concordance rate of quality control metrics of sequenced libraries and identify variants and biomarkers between FFPE and FF tissues. The Illumina