Morphology and Natural History of Familial Adenomatous Polyposis (FAP)-Associated Dysplastic Fundic Gland Polyps (FGPs)
Wen Yih Liang, Thomas Arnason, Eduardo Alfaro, Paul Kelly, Muriel Genevay, Robert D Odze, Gregory Y Lauwers. Massachusetts General Hospital, Boston, MA; Brigham and Women's Hospital, Boston, MA
Background: Up to 90% of patients with FAP develop gastric FGPs, which display low grade dysplasia (LGD) in up to 48% of cases. It is unclear if LGD in FGPs in this population carries a significant risk of progression to more advanced neoplasia. The aims of this study were to characterize the morphologic phenotype of dysplasia in FAP-associated FGPs and evaluate their natural history.
Design: All FAP patients with a dysplastic FGP diagnosed from 1999-2008 were identified at 2 hospitals. Slides were reviewed and dysplasia was classified as intestinal, gastric, or mixed phenotype. All follow up biopsies were reviewed. Outcomes were defined as: regression of dysplasia (dysplasia absent at last biopsy); persistent dysplasia (dysplasia of same grade present at last biopsy); progression to a more advanced lesion (diagnosis of higher grade neoplasm, eg. high grade dysplasia [HGD], adenoma, carcinoma); concurrent carcinoma (carcinoma diagnosis <3 months after initial biopsy). Outcomes were compared to FAP patients with FGPs without dysplasia and patients with sporadic gastric dysplasia.
Results: Table 1 shows clinicopathologic features and outcomes in the 3 cohorts. 3 cases of FAP associated FGPs with LGD progressed to 2 adenomas with LGD and 1 intramucosal carcinoma. Dysplasia in FGPs in FAP patients was less frequently associated with intestinal phenotype (p<0.001), HGD (p<0.01), and the finding of concurrent or subsequent carcinoma (p=0.05) when compared to sporadic gastric dysplasia.
|FAP with FGP, no dysplasia (n=15)||FAP with FGP with dysplasia (n=24)||Sporadic dysplasia (n=56)|
|Mean age at first diagnosis of FGP in years (range)||34.8(20-48)||33.6(13-63)||-|
|Mean age at first diagnosis of dysplasia in years (range)||-||35.1(13-64)||65.6(37-95)|
|Phenotype of dysplasia|
|Grade of dysplasia at diagnosis|
|Regression of dysplasia†||-||8(33%)||20(36%)|
|Progression to a more advanced lesion||0||3(13%)||7(13%)|
|Progression to carcinoma||0||1(4%)||7(13%)|
|Mean length of follow up in years (range)||3.3(0-10.3)||6.1(0.8-12.6)||2.6(0-11.3)|
|Mean number of endoscopies (range)||1.6(1-5)||5.7(2-22)||40 patients had ≥ 1 follow up biopsy|