Cytologic evaluation of brushing specimens obtained from the colon may be u
seful in the diagnosis of neoplastic and inflammatory lesions, as previous
studies have reported favorable sensitivity and specificity figures for thi
s procedure. In this study, we report our experience with 80 colonic brushi
ngs examined over a 5-yr period. Thirty cases received an atypical or malig
nant cytologic diagnosis. Nineteen of 20 cases diagnosed cytologically as a
denocarcinoma revealed adenocarcinoma on biopsy; one case showed only adeno
matous epithelium on biopsy and subsequent resection. Cases diagnosed cytol
ogically as "atypical" or "adenomatous" showed adenocarcinoma, adenoma, and
inflammatory conditions upon biopsy.
Slides from 30 atypical/malignant cases were retrospectively reviewed for a
number of cytomorphologic features and were correlated with the histologic
diagnosis. Cases from histologically confirmed adenocarcinoma tended to sh
ow greater degrees of altered nuclear polarity, nuclear pleomorphism, membr
ane irregularities, and chromatin pattern alterations than those from histo
logically proven adenomatous or inflammatory lesions. The most likely cause
of a false-positive diagnosis in this setting is sampling of an adenoma wi
th high-grade dysplasia which fails to meet histologic criteria for adenoca
rcinoma (invasion of the underlying muscularis mucosae). Thus, in the secon
d part of the study, we examined histologic sections from surgically excise
d adenomas to determine the frequency with which profound nuclear atypia is
at least focally present, potentially resulting in a false-positive cytolo
gy diagnosis upon brushing. Slides from 51 cases were reviewed; cytologic a
typia beyond that typically observed in adenomas was not observed in 43% of
cases. However, profound nuclear atypia was present in 6% of cases; cytolo
gic evaluation of a brushing specimen from these lesions may have resulted
in a false-positive diagnosis of adenocarcinoma, despite the histologic dia
gnosis of adenoma with severe dysplasia. The remaining cases demonstrated i
ntermediate degrees of atypia. These findings serve to quantitate the frequ
ency with which cytohistologic discrepancies might be expected for mass les
ions of the colon. (C) 2001 Wiley-Liss, Inc.