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?
BACKGROUND
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."


METHODS
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.
Krishnamurti
Uma
U
Department of Pathology, University of Pittsburgh Medical Center-Presbyterian, Pittsburgh, PA 15213, USA.
Sasatomi
Eizaburo
E
Swalsky
Patricia A
PA
Finkelstein
Sydney D
SD
Ohori
N Paul
NP
D000230:Adenocarcinoma / Q000175:diagnosis / Q000235:genetics* / Q000473:pathology*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000483:Alleles; D001650:Bile Duct Neoplasms / Q000175:diagnosis / Q000235:genetics* / Q000473:pathology*; D004273:DNA, Neoplasm / Q000235:genetics; D005188:False Negative Reactions; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D011905:Genes, ras / Q000235:genetics; D006801:Humans; D019656:Loss of Heterozygosity / Q000235:genetics*; D008297:Male; D018895:Microsatellite Repeats / Q000235:genetics; D008875:Middle Aged; D009154:Mutation / Q000235:genetics; D010865:Pilot Projects; D011379:Prognosis; D012680:Sensitivity and Specificity
D004273:DNA, Neoplasm