Choosing specimens for NGS

Next-generation sequencing reads a tumor’s DNA for mutations, but the test can fail before it starts if the wrong tissue is used. Mayo Clinic Laboratories has published new guidance on choosing pathology specimens that leave enough material for molecular and cytogenetic testing in solid tumors. (news.mayocliniclabs.com) The guidance was posted March 23, 2026, as a Mayo Clinic Laboratories microlearning module on “Selecting Pathology Specimens for Solid Tumors Next-Generation Sequencing.” It says specimen source, fixation method, cellularity, tumor amount, and tumor percentage all affect DNA quality, assay performance, and result reliability. (news.mayocliniclabs.com) In practice, the problem is often scarcity: one biopsy may need to cover diagnosis, immunostains, cytogenetics, and sequencing. Mayo’s module says it uses real laboratory examples and a structured review process to help teams decide which slide, block, or cytology sample should be preserved for downstream testing. (news.mayocliniclabs.com) Mayo’s own solid-tumor sequencing requirements show how narrow the margin can be. Its MayoComplete Solid Tumor Panel requires at least 20% tumor nuclei, with 40% preferred, and its tissue requirements document says the goal is to avoid delays and improve the odds of generating a sequencing result. (testcatalog.org) (mayocliniclabs.com) The new explainer also fits a broader shift in pathology workflows toward using cytology for molecular work when surgical tissue is limited. Mayo has said cytology specimens can support molecular analysis in solid tumors and has built education around cytology-to-molecular workflows over the past year. (news.mayocliniclabs.com) That matters most in cancers where patients may only have a small needle sample. Mayo says its lung cancer next-generation sequencing panel accepts cytology and uses reduced formalin-fixed, paraffin-embedded tissue requirements so more patients can get results. (news.mayocliniclabs.com) The underlying lab issue is preanalytics — everything that happens before sequencing starts. A 2022 review in *Clinics in Laboratory Medicine* said specimen choice, procurement, processing, and matching the sample to the test platform all shape whether molecular oncology testing succeeds. (labmed.theclinics.com) Mayo has been building toward this for years. A 2018 validation study involving Mayo authors reported that multiple cytology specimen types were equivalent, and in some settings superior, to formalin-fixed, paraffin-embedded tissue for next-generation sequencing workflows. (sciencedirect.com) The practical message is less about a new machine than about triage at the bench. Mayo’s latest guidance tells pathologists and lab teams to treat every fragment of tumor tissue as finite, because the right specimen choice can determine whether sequencing happens at all. (news.mayocliniclabs.com)