Comparison of dysplastic fundic gland polyps in patients with and without familial adenomatous polyposis

Aims Dysplastic fundic gland polyps (d‐ FGP s) typically arise in patients with familial adenomatous polyposis ( FAP ) but may occur in non‐syndromic patients. They rarely become malignant, but their significance is unclear, especially in non‐syndromic patients. We aimed to compare d‐ FGP s in patients with and without FAP , using clinicopathologic findings and β‐catenin immunohistochemistry ( IHC ). Methods and results We identified 124 fundic gland polyps with low‐grade dysplasia ( LGD ) or high‐grade dysplasia ( HGD ) or indefinite for dysplasia ( IFD ) from 66 patients (27 with FAP ; 39 non‐syndromic). We recorded patient sex, age at first d‐ FGP , time until subsequent d‐ FGP (if any), history of non‐gastric cancer (no patients had gastric cancer), proton‐pump inhibitor use, and the presence of Helicobacter pylori . β‐Catenin IHC was performed on cases with available blocks. The mean age at d‐ FGP diagnosis was 31 years for FAP patients and 61 years for non‐syndromic patients ( P < 0.0001). Sixteen FAP patients (59%) developed at least one subsequent d‐ FGP , as compared with 10 (27%) non‐syndromic patients ( P = 0.0099). The median time between d‐ FGP detection was 11.5 months in FAP patients and 7 months in non‐syndromic patients ( P = 0.82). Six FAP patients (22%) and 17 non‐syndromic patients (44%) had non‐gastric malignancies ( P = 0.11). β‐Catenin IHC showed nuclear positivity in 14 of 112 (13%) d‐ FGP s: 12 of 94 with LGD , two of three with HGD , and none of 15 with IFD polyps. Conclusions Familial adenomatous polyposis patients develop d‐ FGP s earlier and more often develop additional ones than non‐syndromic patients. d‐ FGP s in FAP and non‐syndromic patients have similar low rates of β‐catenin nuclear IHC positivity. FAP and non‐syndromic patients developed non‐gastric cancers at similar rates, suggesting that d‐ FGP s may portend a general increased risk of carcinogenesis in non‐syndromic patients.