Adenocarcinoma in colonic brushing cytology: High-grade dysplasia as a diagnostic pitfall

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.