Gastric hepatoid adenocarcinomas are a genetically heterogenous group; most tumors show chromosomal instability, but MSI tumors do exist

• Published in: Human pathology 2019-06, Vol.88, p.27-38
• Main Authors: Tsuruta, Shinichi, Ohishi, Yoshihiro, Fujiwara, Minako, Ihara, Eikichi, Ogawa, Yoshihiro, Oki, Eiji, Nakamura, Masafumi, Oda, Yoshinao
• Format: Article
• Language: English
• Subjects: Adenocarcinoma - chemistry; Adenocarcinoma - genetics; Adenocarcinoma - pathology; Aged; Aged, 80 and over; Biomarkers; Biomarkers, Tumor - analysis; Cancer therapies; Chemotherapy; Chromosomal instability; Chromosomal Instability - genetics; Cyclin-Dependent Kinase Inhibitor p16 - analysis; Cyclin-Dependent Kinase Inhibitor p16 - genetics; Female; Gastric cancer; Gene Expression; Hepatoid adenocarcinoma; Humans; Immunohistochemistry; Liver cancer; Male; Metastasis; Microsatellite Instability; Middle Aged; Molecular subtype; Morphology; Mutation; Radiation therapy; Ribonucleoproteins, Small Nucleolar - analysis; Ribonucleoproteins, Small Nucleolar - genetics; Stomach Neoplasms - chemistry; Stomach Neoplasms - genetics; Stomach Neoplasms - pathology; Tumors
• ISSN: 0046-8177; 1532-8392
• DOI: 10.1016/j.humpath.2019.03.006

The Cancer Genome Atlas Research Network classified gastric adenocarcinoma into four molecular subtypes: (1) Epstein-Barr virus–positive (EBV), (2) microsatellite-instable (MSI), (3) chromosomal instable (CIN), and (4) genomically stable (GS). The molecular subtypes of gastric hepatoid adenocarcinomas are still largely unknown. We analyzed 52 hepatoid adenocarcinomas for the expression of surrogate markers of molecular subtypes (MLH1, p53, and EBER in situ hybridization) and some biomarkers (p21, p16, Rb, cyclin D1, cyclin E, β-catenin, Bcl-2, IMP3, ARID1A and HER2), and mutations of TP53, CTNNB1, KRAS, and BRAF. We analyzed 36 solid-type poorly differentiated adenocarcinomas as a control group. Hepatoid adenocarcinomas were categorized as follows: EBV group (EBER-positive), no cases (0%); MSI group (MLH1 loss), three cases (6%); “CIN or GS” (CIN/GS) group (EBER-negative, MLH1 retained), 49 cases (94%). In the CIN/GS group, most of the tumors (59%) had either p53 overexpression or TP53 mutation and a coexisting tubular intestinal-type adenocarcinoma component (90%), suggesting that most hepatoid adenocarcinomas should be categorized as a true CIN group. Hepatoid adenocarcinomas showed relatively frequent expressions of HER2 (score 3+/2+: 21%/19%). Hepatoid adenocarcinomas showed shorter survival, more frequent overexpressions of p16 (67%) and IMP3 (98%) than the control group. None of hepatoid adenocarcinomas had KRAS or CTNNB1 mutations except for one case each, and no hepatoid adenocarcinomas had BRAF mutation. In conclusion, gastric hepatoid adenocarcinomas are a genetically heterogenous group. Most hepatoid adenocarcinomas are “CIN,” but a small number of hepatoid adenocarcinomas with MSI do exist. Hepatoid adenocarcinomas are characterized by overexpressions of p16 and IMP3. •Gastric hepatoid adenocarcinomas are a genetically heterogenous group.•Most hepatoid adenocarcinomas are chromosomal instable, but a small number of hepatoid adenocarcinomas with MSI do exist.•Hepatoid adenocarcinomas are characterized by overexpression of p16 and IMP3, which probably contribute to the aggressive behavior.