Comparative molecular analysis of loss of heterozygosity in adenocarcinoma in bile duct brushings and corresponding surgical pathology specimens

Precision cytopathology: expanding opportunities for biomarker testing in cytopathology

Precision cytopathology refers to therapeutically linked biomarker testing in cytopatology, a dynamically growing area of the discipline. This review describes basic steps to expand precision cytopathology services. Focusing exclusively on solid tumors, the review is divided into four sections: Section 1: Overview of precision pathology- opportunities and challenges; Section 2: Basic steps in establishing or expanding a precision cytopathology laboratory; Section 3: Cytopathology specimens suitable for next generation sequencing platforms; and Section 4: Summary. precision cytopathology continues to rapidly evolve in parallel with expanding targeted therapy options. Biomarker assays (companion diagnostics) comprise a multitude of test types including immunohistochemistry, in situ hybridization and molecular genetic tests such as PCR and next generation sequencing all of which are performable on cytology specimens. Best practices for precision cytopathology will incorporate traditional diagnostic approaches allied with careful specimen triage to enable successful biomarker analysis. Beyond triaging, cytopathologists knowledgeable about molecular test options and capabilities have the opportunity to refine diagnoses, prognoses and predictive information thereby assuming a lead role in precision oncology biomarker testing.

FISHing for pancreatobiliary tract malignancy in endoscopic brushings enhances the sensitivity of routine cytology

Pancreatobiliary tract carcinoma is a lethal disease with low survival rates and limited treatment options. Diagnosis is complicated by benign conditions that can mimic malignancy on radiological studies (e.g. primary sclerosing cholangitis or PSC) and the suboptimal sensitivity of endoscopic biopsy/brushings obtained by endoscopic retrograde cholangiopancreatography (ERCP). The detection of multiple chromosomal gains by fluorescence in situ hybridization (FISH), referred to as polysomy, has demonstrated improved sensitivity over routine cytological evaluation. The evaluation of brushings by both routine cytology and FISH in our cytopathology laboratory has been in clinical practice since 2003. Strong morphological and screening skills enable cytotechnologists to become proficient in the assessment of FISH slides, which translates into cost and time savings. Multiple reports from various institutions have demonstrated the utility of FISH for patients with and without PSC. The incorporation of routine cytology and FISH results into the management algorithm for patients under suspicion for pancreatobiliary malignancy is a testament to the clinical success of these cytological assays.

Identification of malignant cytologic criteria in pancreatobiliary brushings with corresponding positive fluorescence in situ hybridization results

Cytologic evaluation of pancreatobiliary brushings is specific but poorly sensitive for malignancy. Detection of polysomic cells by fluorescence in situ hybridization (FISH) is significantly more sensitive than routine cytology with similar specificity. The purpose of this study was to identify cytologic criteria most associated with malignancy in specimens unaffected by sample failure. Endoscopic brushings were split equally for routine cytologic and FISH analyses per clinical practice. We retrospectively evaluated 16 cytologic criteria on Papanicolaou-stained slides. We assumed that the presence of polysomic cells by FISH indicated successful tumor sampling in specimens from patients with pathologic evidence of malignancy on follow-up. We compared cytologic criteria of malignant brushings with corresponding positive FISH results (positive control, n = 39) with those without evidence of malignancy and corresponding negative FISH results (negative control, n = 30). The presence of single abnormal cells, irregular nuclear membranes, and enlarged nuclei were independent predictors of malignancy by logistic regression (P < .05).

Analysis of loss of heterozygosity in atypical and negative bile duct brushing cytology specimens with malignant outcome: are "false-negative" cytologic findings a representation of morphologically subtle molecular alterations?

CONTEXT

Conventional cytologic evaluation of bile duct brushings for neoplasia has high specificity but relatively low sensitivity.

OBJECTIVE

The aim of this pilot study was to examine whether K-ras mutations and loss of heterozygosity for multiple microsatellite markers in bile duct brushings would contribute to the detection of malignancy in cases initially reported as "negative" or "atypical."

DESIGN

Bile duct brushing specimens with a negative or an atypical cytologic result (9 cases) had a benign result on the surgical pathology specimen, and 9 additional negative or atypical cases demonstrated adenocarcinoma on the resected surgical specimen. Cells from representative cytopathology and histology slides were microdissected and analyzed for K-ras mutations and for loss of heterozygosity with a panel of 15 polymorphic markers on chromosomes 1p, 3p, 5q, 9p, 9q, 10q, 17p, and 22q.

RESULTS

Among cytology cases with malignant outcome, loss of heterozygosity or K-ras mutation was detected in 8 (88.8%) of 9 cases. In the corresponding 9 surgical pathology specimens with adenocarcinoma, K-ras mutations and/or allelic losses were detected in all (100%). Loss of heterozygosity or K-ras mutation was not detected in cytology cases that had a benign surgical outcome. The fractional allelic loss of these 9 cytology specimens ranged from 0 to 0.25 (mean, 0.14). This compared with the fractional allelic loss ranging from 0.15 to 0.42 (mean, 0.27) for the corresponding surgical specimens.

CONCLUSIONS

This pilot study suggests that low-level fractional allelic loss or K-ras mutation in the negative/atypical cytology samples with malignant outcome is a representation of morphologically subtle molecular alterations.

K-Ras and microsatellite marker analysis of fine-needle aspirates from intraductal papillary mucinous neoplasms of the pancreas

Preoperative diagnosis of pancreatic cystic lesions is difficult despite the combination of cytomorphology, radiographic imaging characteristics, and fluid tumor markers such as carcinoembryonic antigen. Intraductal papillary mucinous neoplasms (IPMNs) represent a subset of preinvasive pancreatic cystic neoplasms and are associated with accumulated genetic mutations, especially K-ras and tumor suppressor genes such as p53. Application of molecular techniques to cyst fluid obtained by endoscopic ultrasound guided fine-needle aspiration (EUSFNA) may contribute to preoperative assessment. Sixteen patients with pancreatic cystic lesions had cyst fluid obtained by preoperative pancreatic EUSFNA or intraoperative aspiration. All patients subsequently underwent surgical resection of the pancreas and IPMN was documented in all (6 adenomas, 6 borderline tumors, and 4 carcinomas). DNA was extracted from the cyst fluids and mutational analysis for K-ras point mutations and loss of heterozygosity (LOH) analysis using a preselected panel of genomic loci were performed. LOH was observed in 3 of 4 carcinomas as compared to 4 of 11 adenomas and borderline lesions (1 was QNS). LOH and K-ras mutations were both acquired in 2 of 4 carcinomas and in 1 of 12 adenoma/borderline lesions. Although the study is small, molecular analysis for LOH and K-ras mutations is useful in the preoperative evaluation of cystic pancreatic lesions. Increasing degree of neoplasia appears to correlate with increased genetic abnormality using a panel of selected genomic markers.

Accumulation of beta-catenin protein, mutations in exon-3 of the beta-catenin gene and a loss of heterozygosity of 5q22 in solid pseudopapillary tumor of the pancreas

BACKGROUND

Solid pseudopapillary tumors (SPT) of the pancreas are neoplasms with a low malignant potential. The molecular events contributing to the pathogenesis of SPTs are still unknown.

OBJECTIVES

This study was intended to help better understand the early steps of human SPT development.

METHODS

We microdissected 20 SPTs and normal pancreatic tissue. In addition, we examined the DNA from each SPT for mutations in exon-3 of beta-catenin and loss of heterozygosity (LOH) on 9 chromosome arms using 10 microsatellite markers. Immunohistochemical staining for beta-catenin was performed.

RESULTS

Activating mutations between codons 32 and 37 of beta-catenin exon-3 were present in 16 cases (80%). Allelic loss on chromosome 5q22.1 was present in 10 cases (55.5%), while no allelic loss was found on chromosomes 1p, 6q, 9p, 9q, 11p, 11q, 17p, or 22q. Nuclear accumulation of beta-catenin was found in 20 cases (100%).

CONCLUSION

Mutations in exon-3 of the beta-catenin gene, nuclear accumulation of beta-catenin, and LOH on chromosome 5q22.1 in SPT tissue suggest that these mutations are involved in SPT tumorigenesis.