To determine if a simple prewash step added to the processing workflow of tissue procurement by a core needle biopsy device will recover enough cells to expand the laboratory testing armamentarium. Tissue was obtained from unfixed resection specimens using a core needle device and washed in a buffered solution before fixation. This creates a liquid aliquot from which dislodged cells can be kept and separated from the tissue specimen, the latter of which can then undergo traditional formalin-fixed, paraffin-embedded processing. Cells dislodged from the tissue during the biopsy procedure are recoverable, are representative of the tissue section and of sufficient quantities for additional laboratory testing. The core needle biopsy wash is an under-recognised and underutilised approach to extending the diagnostic capabilities of the limited amount of targeted material obtained during this common procedure. The ability to recover supplemental amounts of diagnostic material yields great potential as a substrate for a multitude of current and developing laboratory assays. © Author(s) (or their employer(s)) 2022. No commercial re-use. See rights and permissions. Published by BMJ.