Phenotypic heterogeneity of hereditary diffuse gastric cancer: report of a family with early-onset disease

Background and Aims: The time course for the development of clinically significant hereditary diffuse gastric cancer (HDGC) is unpredictable. Little is known about the progression from preclinical, indolent lesions to widely invasive, aggressive phenotypes. Gastroendoscopy often fails to detect early lesions, and risk-reducing/ prophylactic total gastrectomy (PTG) is the only curative approach. We present an HDGC family with early- onset disease in which clinical and histologic findings provided insight into the understanding of different HDGC phenotypes. Methods: The proband was diagnosed at age 18 years with widely invasive, metastatic DGC. CDH1 genetic testing identified a pathogenic, germline CDH1 variant (c.1901C>T, p.Ala634Val). Thirty family members were tested, and 15 CDH1 carriers were identified. Results: Six family members had PTG, with negative preoperative workup. The proband’s 14-year-old sister is the youngest patient, reported to date, to have PTG after negative preoperative biopsy sampling. Intramucosal HDGC foci were detected in all PTG specimens (1-33). In contrast to the “indolent” phenotype of these foci, the aggressive DGC from the proband showed pleomorphic cells, absent E-cadherin expression, increased proliferation (Ki-67 index), and activation of oncogenic events (p53, pSrc and pStat3 overexpression). All family members had Helicobacter pylori gastritis. Cag-A–positive strains were detected in all specimens, except in the proband’s sister. Conclusions: HDGC is a heterogeneous disease regarding clinical behavior, endoscopic findings, histopathologic features, and immunophenotypic/molecular profile. The presence of bizarre, pleomorphic cells in endoscopic biopsy specimens is suggestive of advanced disease and should prompt clinical intervention. The involvement of a full multi- disciplinary team is essential for the management of these patients. (Gastrointest Endosc 2018;87:1566-75.)