Left sided colorectal adenomatous polyps have more risk for high grade dysplasia.

Colorectal cancer is the second leading cause of cancer death worldwide. Through risk assessment of malignancy in polyps, screening programs can achieve the best results. This study aimed to determine the association between the grade of dysplasia and the location of colorectal polyps. 240 colorectal adenomatous polyps which were referred to department of pathology at Rasoul-e-Akram Hospital between 2005 and 2009 met the inclusion criteria. Demographic data and information about size of polyps, grade of dysplasia and location of polyps were collected and analyzed by Chi-square and t-test. 124 (58.8%) patients were male and 87 (41.2%) were female. The mean age of the patients was 61.6 years. 47 (19.6%) polyps were right-sided and 193 (80.4%) were left sided. 39 (16.2%) polyps had high grade dysplasia. 27 (12.8%) patients had 56 synchronous polyps (23.3%). 176 (73.3%), 39 (16.2%) and 25 (10.5%) polyps were of tubular, tubulovillous and villous types respectively. The greatest dimension of 110 (45.8%) polyps was <0.5 cm, 97 (40.4%) 0.5-1 cm, 22 (9.2%) between 1 and 2 cm and finally 11 (4.6%) >2 cm. High grade dysplasia was detected in 3 (6.3 %) of right-sided and 36 (18.6%) of left-sided polyps. The obtained results revealed that size of polyp and amount of villous component were strongly associated with high grade dysplasia. Left side location of polyps was independently associated with high grade dysplasia. Left-sided colorectal polyps must be treated more seriously, especially the larger ones with villous component. There was no association between age and gender and the grade of dysplasia.