A Multicenter Investigation of Minimally Invasive Sample Processing and the Pre-Analytic Assessment of NSCLC Small Biopsy Specimens for Molecular Testing.

: In the era of precision oncology, the management of lung cancer depends fundamentally on the acquisition of sufficient neoplastic material for both definitive histological subtyping and comprehensive molecular profiling. This study aimed to investigate molecular testing adequacy rates for small lung biopsy specimens obtained via minimally invasive procedures at three high-volume oncology centers. Recognizing that a significant subset of specimens remains insufficient for analysis, we evaluated the utility of cell pellets derived from residual fixative media as a supplemental resource for ancillary molecular testing. : Over a six-month period, specimen handling workflows for small biopsies were assessed across three high-volume oncology centers. The pre-analytic molecular adequacy of formalin-fixed paraffin-embedded (FFPE) tissue sections from patients diagnosed with non-small cell lung cancer (NSCLC) was evaluated. During the final two months of the study, in cases where the primary FFPE tissue was deemed inadequate for molecular profiling, the residual fixative solution was recovered and processed to generate supplemental cell pellets. : Using adequacy thresholds of >200 tumor cells per section and a tumor cell fraction (TCF) of ≥10% or ≥5% (depending on specific assay requirements), the overall adequacy rates for FFPE samples were 80.6% (2986/3705) and 88.9% (3293/3705), respectively. During the final two months, 18.9% (154/816) of cases exhibited inadequate FFPE sections. However, of these cases, 56% (86/154) yielded adequate cell pellets based on cellularity evaluation and DNA quantification. These results indicate that cell pellets collected from the fixative medium of thoracic small biopsies are a valuable supplemental material for ancillary testing. : This multi-center investigation demonstrates that a notable subset of NSCLC specimens obtained via minimally invasive biopsy remains insufficient for molecular analysis. Cell pellet samples obtained from residual fixative media serve as a critical supplemental resource, effectively increasing the success rate of molecular adequacy in clinical practice.