According to the published medical literature to date, prophylactic gastrectomy undertaken in the context of carriage of a germline truncating E-cadherin mutation and an appropriate positive family history will lead to the discovery of occult foci of adenocarcinoma in all gastrectomy specimens. We describe the first published case of a patient whose prophylactic gastrectomy in this setting failed to reveal any dysplastic or malignant foci. Furthermore the patient's nephew, who was found to carry an identical E-cadherin mutation on family screening and also underwent prophylactic gastrectomy, was shown to have multi-focal diffuse adenocarcinoma after analysis of the gastrectomy specimen. Both patients were also found to have penetrant genetic haemochromatosis. Within this case, we discuss the clinical manifestations and penetrance of germline E-cadherin mutations and the difficult decisions facing both clinicians and families with this mutation. We also speculate on how these patients' undiagnosed genetic haemochromatosis may have influenced the pathology encountered.