Gardner Fibroma: Clinical and Histopathologic Implications of Germline APC Mutation Association

The proportion and clinical characteristics of Gardner fibromas (GAFs) that are sporadic versus familial adenomatous polyposis (FAP)-associated have not been clearly established. We report on 7 patients diagnosed with GAF who underwent APC sequencing and duplication/deletion testing. Three (43%) were found to have underlying APC germline perturbations consistent with FAP; these patients had multifocal (1) or large; unresectable (2) GAFs. The 4 patients with negative APC testing each had a single resectable GAF. β-catenin reactivity was noted in all FAP-associated GAFs and in 1/4 APC wild-type cases. FAP-associated GAFs may be less common than sporadic GAFs and can demonstrate clinically distinct features.