The role of liquid-based cytology in the investigation of colorectal lesions: a cytohistopathological correlation and evaluation of diagnostic accuracy

The role of cytologic techniques is not widely accepted even if it is well documented that the cytologic investigation of colorectal tract could complement the biopsy and increase the correct diagnosis of carcinomas. This study aims to evaluate the role of Thin-Prep(R) liquid-based cytology in the investigation of colorectal lesions. We compared the diagnostic accuracy of Thin-Prep(R) with that of biopsy in 158 patients with signs and symptoms of the lower gastrointestinal tract. Each patient underwent colonoscopy, followed by tissue biopsy and brush cytology. Brushing material was obtained and prepared according to the operating manual of Thin-Prep(R). The rate of unsatisfactory smears was 5% (8/158) with liquid-based technique and appeared to be slightly higher than the respective of biopsy [3.2% (5/158) (5 vs 3.2%, P = 0.18)]. Based on the final diagnosis, 89 out of 93 total malignant cases and 53 out of 53 total benign cases were correctly diagnosed with Thin-Prep(R) technique (four false negatives). Accurate diagnosis with biopsy was performed in 87 out of 93 total malignant cases and 53 out of 53 total benign cases with biopsy (six false negatives). Neither in Thin-Prep(R) technique nor in biopsy were false-positive cases observed. The sensitivities of detecting malignancy by Thin-Prep(R) and biopsy were 95.7, and 93.5%, respectively (no significant difference, P = 0.239). The sensitivity was augmented (98.9%) when the two techniques were combined, and this difference was found to be statistically significant (98.9 vs 92.9, P = 0.01, and 98.9 vs 95.7, P = 0.039). Liquid-based cytology appears to be an easy, highly accurate, and reliable cytologic method for the diagnostic approach of colorectal diseases and could be applied as complementary to biopsy for the improvement of the diagnosis. Moreover, could be used for DNA ploidy analysis and immmunohistochemical studies.