Nonconventional dysplasia in patients with inflammatory bowel disease and colorectal carcinoma: a multicenter clinicopathologic study

Several types of nonconventional dysplasia have been recently described in inflammatory bowel disease (IBD). However, strict morphologic criteria are lacking, and their clinicopathologic features (including potential association with conventional dysplasia and/or colorectal cancer [CRC]) are poorly understood. A total of 106 dysplastic or serrated lesions in 58 IBD patients with CRC were retrospectively identified from five institutions. Thirty-six cases of nonconventional dysplasia were identified in 26 (45%) of the 58 patients and occurred with similar frequency in men and women (58% and 42%, respectively), with a mean age of 54 years (range: 24–73) and a long history of IBD (mean: 17 years, range: 2–43). Six morphologic patterns were recognized. Hypermucinous dysplasia ( n = 15; 42%) presented as either a ‘pure type’ ( n = 5; 14%) or a ‘mixed type’ with either conventional or another nonconventional subtype ( n = 10; 28%). Serrated lesions, as a group, were equally common ( n = 15; 42%) and included three variants: traditional serrated adenoma-like ( n = 10; 28%), sessile serrated lesion-like ( n = 1; 3%), and serrated lesion, not otherwise specified ( n = 4; 11%). Dysplastic lesions with increased Paneth cell differentiation ( n = 4; 11%) and goblet cell deficient dysplasia ( n = 2; 6%) were rare. Twelve (46%) of the 26 patients had only nonconventional dysplasia, whereas the remaining 14 patients (54%) had both nonconventional and conventional dysplasias. Nonconventional dysplasia was most often graded as low-grade dysplasia (81%), which was less common in conventional dysplasia (37%) ( p = 0.003). When present alone, nonconventional dysplasia was predominantly found in the left colon (81%, p = 0.006) as a polypoid or raised lesion (75%, p