[Clinicopathological features of gastric adenocarcinoma with enteroblastic differentiation: a report of twelve cases]

Objective: To investigate the clinicopathological features, immunophenotype, diagnosis and differential diagnosis of gastric adenocarcinoma with enteroblastic differentiation (GAED). Methods: Twelve cases of GAED diagnosed in Fujian Provincial Hospital from August 2019 to August 2020 were collected. HE staining, immunohistochemistry and HER2 gene amplification were evaluated. In addition, 343 cases of gastric adenocarcinoma diagnosed in the same period were used as the control group to compare the clinicopathological differences between them. Results: The 12 cases of GAED included 10 males and 2 females, aged 59-75 years (median 66.5 years). The main clinical manifestations were abdominal pain, melena with hematemesis; nine tumors were ulcerative and three were protuberant. The tumor diameter ranged from 1.5 to 9.5 cm (median 6.0 cm). Histologically, the tumor cells were arranged in tubular, papillary, cribriform, or adenoid structures. The cells were cuboidal to columnar, with relatively distinct cell boundaries and abundant clear or slightly eosinophilic cytoplasm. Immunohistochemically, tumor cells were positive for SALL4 (12/12), glypican-3 (9/12), AFP (5/12), CDX2 (8/12), CD10 (3/12), p53 mutated (10/12), HER2 (2/12, 3+), and both cases showed HER2 gene amplification by fluorescence in situ hybridization. Compared with common gastric adenocarcinoma, GAED showed higher rate of vascular invasion and tumor progression (P<0.05), but there were no significant differences in age, sex, degree of differentiation, nerve invasion, lymph node metastasis, pT stage, pN stage and pM stage (P>0.05). Conclusions: GAED is a rare type of gastric adenocarcinoma. Pathologically, GAED has both embryonal and intestinal phenotypes. In terms of biological behavior, it is more invasive. GAED needs to be distinguished from common gastric adenocarcinoma in clinical diagnosis.