Effusion fluids useful for molecular FISH
An effusion cytology thread highlighted ascitic and bile fluids as rich sources for molecular testing—FISH and other assays can help diagnose indeterminate biliary strictures and identify prognostic/therapeutic markers. That reinforces the need for rigorous cell‑block prep and nucleic acid preservation in body‑fluid handling. (x.com)
A 2025 Henry Ford retrospective on 228 biliary brushing specimens reported cytology sensitivity 45.8% versus FISH sensitivity 84.2% and FISH specificity 96.0%, highlighting a large sensitivity gain when FISH is added to routine cytology. (scholarlycommons.henryford.com) A single-center prospective study (April 2019–January 2021) of 102 patients found FISH raised sensitivity for malignant biliary strictures from 36.1% to 50.7% while specificity remained similar, with 74 of 102 strictures ultimately malignant on follow-up. (mdpi.com) Commercial clinical FISH panels for pancreatobiliary specimens target chromosomal gains in chromosomes 3, 7 and 17 as aneuploidy markers associated with malignancy and are offered by reference labs as an adjunct to brushing/aspirate cytology. (mlabs.umich.edu) Practical specimen-volume guidance for cell‑block and molecular work: minimum aspirate recommendations range from 20 mL for routine cytology to 30–50 mL optimal for cell‑block preparation and many labs request 50–75 mL when possible to maximize cellularity for ancillary testing. (ubc-pathology.sites.olt.ubc.ca) Pre‑analytic variables alter nucleic acid yield: an AJCP study showed collection media choice and delayed processing reduced RNA/DNA quality, and multiple laboratory SOPs recommend refrigeration or alcohol‑based fixatives (e.g., CytoLyt) and, where advised, heparin or RPMI for short‑term transport to preserve downstream molecular assay performance. (academic.oup.com) Contemporary reviews conclude well‑prepared FFPE cell blocks support FISH, IHC, PCR and NGS on effusion material, with validated methods ranging from formalin‑alcohol cell‑block techniques to automated Cellient processing to optimize morphology and molecular compatibility. (sciencedirect.com)
