Indeterminate Biliary Stricture: Biliary Brushing with Atypical Cells
A 67-year-old man with a 2.5-cm hilar stricture and painless jaundice undergoes ERCP with biliary brushing. The cytology shows cohesive clusters of ductal cells with mild nuclear enlargement, slight loss of polarity, and a clean background. The cytotechnologist and pathologist agree the findings are 'atypical, cannot exclude malignancy.' CA19-9 is elevated at 180 U/mL; imaging shows a stricture without a discrete mass and no lymphadenopathy. The gastroenterologist calls the cytology laboratory wanting to know whether the atypical brushing is diagnostic of cholangiocarcinoma and whether he should proceed to surgery or repeat the brushing.
1. How should the atypical brushing result be interpreted, and what are the limitations of biliary brushing cytology in this setting?
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An 'atypical' biliary brushing is indeterminate, not diagnostic of malignancy. Biliary brushing has high specificity when frankly malignant cells are present, but sensitivity is limited (commonly cited in the range of roughly 40-60% for a single brushing), and reactive/inflammatory atypia in the setting of stents, stones, or cholangitis can mimic neoplasia. The reported features here (mild nuclear enlargement, slight polarity loss, clean background) do not meet criteria for 'suspicious' or 'malignant,' which would require more convincing nuclear atypia, marked anisonucleosis, irregular nuclear membranes, and loss of cohesion. The elevated CA19-9 and hilar stricture raise clinical suspicion but are not cytologic evidence. The correct interpretation is indeterminate: it neither confirms nor excludes cholangiocarcinoma, and it should not by itself drive a major resection.
2. What is the appropriate next step, and how would you communicate the result to the gastroenterologist?
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The appropriate next step is additional tissue/cytologic sampling rather than immediate surgery based on an atypical brushing. Options include repeat brushing with fluorescence in situ hybridization (FISH) for polysomy (which improves sensitivity when added to cytology), brush or forceps biopsy at ERCP, cholangioscopy-directed biopsy, or endoscopic ultrasound-guided fine needle aspiration if a targetable lesion is identified. The communication should explicitly state: (1) the result is indeterminate; (2) a single atypical brushing does not exclude malignancy and does not confirm it; (3) correlation with imaging and clinical context is required; and (4) further sampling, ideally with ancillary FISH and/or directed biopsy, is recommended before committing to resection. The cytology report should use standardized terminology (e.g., 'atypical,' 'suspicious,' 'malignant') so the clinician understands the level of certainty.