The histologic phenotype of the dysplastic lesion juxtaposing colorectal carcinomas was assessed in 100 consecutive colectomy specimens: in 50 patients with inflammatory bowel disease (IBD) and in 50 controls (non-IBD patients). Adenomatous growths (AG) were regarded both Dysplasia Associated Lesion or Mass (DALM) and sporadic adenomas. AGs juxtaposing carcinomas were found in 76% (n = 38) of the IBD cases: 52.3% (20 out of 38) were villous, 28.9% (11 out of 38) serrated, 5.3% (2 out of 38) tubular and the remaining 13.2% (5 out of 38) were mixed AGs. Juxtaposing AGs (sporadic adenomas) were also found in 58% (n = 29) of the control cases: 51.7% (15 out of 29) were villous, 6.9% (2 out of 29) tubular, 3.4% (1 out of 9) serrated and the remaining 37.9% (11 out of 29) were mixed. The majority or 81.2% (31 out of 38) of the dysplastic lesions juxtaposing IBD carcinomas were villous or serrated AGs, but only 55.1% (16 out of 29) in control cases. Serrated AGs in particular accounted for nearly 29% of the non-invasive dysplastic lesions abutting IBD carcinomas but only for 3% in control specimens. It would appear that villous and serrated AGs are the most common non-invasive neoplastic lesions from which IBD carcinomas originate.