pancreatobiliary fish testing
المؤلف:
Kathleen Deska Pagana, Timothy J. Pagana, Theresa Noel Pagana.
المصدر:
Mosbys diagnostic and laboratory test reference
الجزء والصفحة:
15th edition , p668-669
2025-07-26
473
Type of test Microscopic examination
Normal findings
No chromosomal ploidy abnormalities
Test explanation and related physiology
It is sometimes difficult to differentiate benign bile duct strictures from early pancreatobiliary cancer. When a stricture is identified on an endoscopic retrograde cholangiopancreatography (ERCP) cancer must be considered as a possible cause. If an obvious cancer is not seen at the time of ERCP, a brush is repeatedly swept along the bile duct to obtain duct surface cells for conventional cytology to identify cancer cells. In conventional cytology, the brushing specimens are placed on a slide and stained with a Papanicolaou (PAP) stain. Slides are then interpreted by a cytopathologist to determine whether they show features that are positive for malignancy, suspicious for malignancy, atypical (meaning there are cells that are not normal but cannot be definitely ascribed to a neoplastic process), or negative for malignancy.
With the use of fluorescence in situ hybridization (FISH) testing, three chromosome enumeration probes and a gene- specific probe to P16 tumor suppressor gene are able to deter mine whether more than one pair of chromosomes or P16 genes exists in the cells obtained from the brushings of the bile duct during ERCP. If extra copies of two or more of the chromosomes or P16 genes are evident, the cells are considered to be polysomic, which indicates a high chance of malignancy.
Contraindications
• See ERCP.
Potential complications
• See ERCP.
Interfering factors
• Errors in obtaining a good specimen can influence results.
• Cytologic examination is always affected by physician interpretation.
Procedure and patient care
Before
* Explain the procedure to the patient.
• Obtain informed consent from the patient.
• Keep the patient NPO (nothing by mouth) as of midnight the day of the test.
• Follow the procedure for ERCP.
During
• During ERCP, a rounded brush is placed through the accessory lumen of the endoscope and passed repeatedly through the stricture.
• The brush is then swished in a cytology solution for FISH or directly smeared on a slide and preserved for conventional cytology.
After
• Follow the guidelines for ERCP.
Abnormal findings
- Sclerosing cholangitis
- Biliary sclerosis
- Tumor or strictures of the pancreatobiliary duct
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