Study reports ultrarapid detection of BRAF mutations from thyroid FNA rinse fluid
- A Memorial Sloan Kettering Cancer Center team reported in *Cancer Cytopathology* that BRAF p.V600E can be detected from thyroid fine-needle aspiration rinse fluid in hours, using leftover supernatant instead of extra tissue. - In 57 aggressive thyroid carcinoma samples, the Idylla assay succeeded in 91% overall and 90% on supernatant cell-free DNA, with 100% agreement against next-generation sequencing or droplet PCR after failures were excluded. - The study targets anaplastic thyroid carcinoma, where BRAF status can guide dabrafenib-trametinib treatment and speed triage without waiting for cell blocks or surgery (fda.gov)
A thyroid fine-needle aspiration is a thin-needle biopsy, and the rinse fluid left after the sample is processed usually goes unused. A Memorial Sloan Kettering team says that leftover fluid can deliver a same-day BRAF mutation result in aggressive thyroid cancers. (pubmed.ncbi.nlm.nih.gov) The study, published in the May 2026 issue of *Cancer Cytopathology*, tested the Biocartis Idylla platform on supernatant cell-free DNA from residual CytoLyt material. The authors focused on aggressive thyroid carcinomas, including anaplastic thyroid carcinoma and high-grade follicular cell-derived non-anaplastic thyroid carcinoma. (pubmed.ncbi.nlm.nih.gov) BRAF p.V600E is a specific DNA change that can act like a stuck accelerator pedal for tumor growth. In anaplastic thyroid carcinoma, finding that mutation matters because the Food and Drug Administration has approved dabrafenib plus trametinib for patients with BRAF V600E-mutant disease when satisfactory local treatment options are lacking. (fda.gov) (accessdata.fda.gov) The usual problem is time. Standard molecular testing often depends on a cell block, a smear, or surgical tissue, which means processing steps before the mutation test can even start; the supernatant approach skips histologic processing and DNA extraction before running the cartridge assay. (pubmed.ncbi.nlm.nih.gov) The researchers identified 57 samples, including 51 from anaplastic thyroid carcinoma, that were tested by Idylla. Across all sample types, the assay had a 91% overall success rate; for supernatant cell-free DNA alone, the success rate was 90%, compared with 100% for surgical formalin-fixed paraffin-embedded specimens. (pubmed.ncbi.nlm.nih.gov) For the 42 samples that also had a reference test by next-generation sequencing or digital droplet polymerase chain reaction, agreement was 100% after assay failures were excluded. The paper also reported a shorter median turnaround time for supernatant testing than for BRAF V600E immunocytochemistry: 2.86 hours versus 46.7 hours. (pubmed.ncbi.nlm.nih.gov) That timing matters most in anaplastic thyroid carcinoma, the rare thyroid cancer subtype that National Comprehensive Cancer Network patient guidance describes as the least common and most aggressive form. The current NCCN thyroid carcinoma guideline also includes anaplastic carcinoma as a separate management pathway. (nccn.org 1) (nccn.org 2) The idea itself is not entirely new. A 2017 study in *Diagnostic Cytopathology* found that routinely discarded thyroid fine-needle aspiration supernatant could contain amplifiable DNA and might improve diagnostic yield when tested for BRAF mutations. (pubmed.ncbi.nlm.nih.gov) What is new here is the combination of speed, sample type, and clinical setting: aggressive thyroid cancers, a cartridge-based assay, and a workflow built around material already generated during routine cytology. The authors say the approach is accurate and expedient, but the paper still describes a single-center experience that labs would need to validate locally before changing practice. (pubmed.ncbi.nlm.nih.gov) If other centers can reproduce the result, a thyroid needle rinse could become more than a byproduct. It could become the fastest route to a BRAF answer in the patients who need one first. (pubmed.ncbi.nlm.nih.gov)
