BACKGROUND: Herein we report a case of an extremely rare pancreatic adenocarcinoma with enteroblastic differentiation (AED), an underrecognized histological subtype. Moreover, the tumor was mixed with a neuroendocrine carcinoma (NEC), which is also a rare malignancy in the pancreas.
METHODS: The patient was an elderly male who was incidentally diagnosed with a 35 mm-sized pancreatic head tumor and underwent pancreatoduodenectomy. Histopathologically, the tumor was composed of four different types: conventional ductal adenocarcinoma, AED, NEC, and squamous cell carcinoma. Interestingly, p53 overexpression and loss of Rb expression, which are characteristic findings of NEC, were observed in all components. He had been received adjuvant chemotherapy after the surgery, however, he died of bath-related cardiac arrest 14 months after surgery.
CONCLUSIONS: In the stomach, AED, a carcinoma resembling fetal gut epithelium, is a rare but established subtype and is considered a related entity of hepatoid carcinoma (HAC). However, gastric AED and HAC differ to some extent. In contrast to the stomach, extragastric AED, including pancreatic AED, is extremely rare, and its biological features are unclear. A mixed tumor with NEC is a complex phenomenon, but it is occasionally reported in extragastric AED. The histogenesis of mixed AED-NEC can be resolved by determining p53 and Rb status.
CONCLUSIONS: Owing to their rare and novel nature, extragastric AED is under-recognized or confused with HAC. Further studies and the establishment of an extragastric AED classification are required.

In addition to hepatoid adenocarcinoma (HAC), gastric adenocarcinoma with enteroblastic differentiation (GAED) and common adenocarcinoma (COM) could also show hepatoid differentiation, which presents a poor prognosis. To elucidate the histogenesis and development of gastric cancer with hepatoid differentiation, we identified 55 cases by histological morphology and a panel of markers, including α-fetoprotein (AFP), Glypican 3 (GPC3) and SALL4, then clinicopathological parameters, pathomorphological characteristics, mucin phenotypes, molecular features, Immunoscore and survival analysis were assessed. A mixture of three types (COM + GAED + HAC) was most commonly observed in the same case, and typical transitions between each histological subtype were frequently seen. Hyaline globule and pink amorphous substance were often present. HER2 was amplified in 21.8% of cases. All the tumors showed intestinal phenotype (69.1%) and mixed gastric/intestinal phenotype (30.9%) and were all defined to chromosomal instable (CIN)/genomically stable (GS) group. Considering that 83.6% cases presented TP53 gene mutation phenotype and 61.8% cases showed ≥10% aberrant E-cadherin expression, the precise molecule classification is ambiguous. Survival analysis showed that patients with high SALL4 expression, high preoperative serum AFP level, or low Immunoscore had a significantly poor overall survival (OS). Moreover, SALL4, HER2, and Immunoscore had an independent influence on OS. In conclusion, we suggest that the development of gastric adenocarcinoma with hepatoid differentiation might a continuously progressive profile: from intestinal-type COM adenocarcinoma to GAED and then HAC. CIN/GS subtypes might be where they belonged. SALL4, HER2, and Immunoscore may be potential therapeutic targets.

Gastric adenocarcinoma with enteroblastic differentiation (GAED) is rare, highly malignant, and has higher vascular invasion and metastasis rates than conventional differentiated gastric cancer (CDGC). We report two cases of GAED that underwent curative resection by endoscopic submucosal dissection (ESD). Case 1 was an 82-year-old man with an elevated lesion in the gastric cardia. Biopsy revealed well-differentiated tubular adenocarcinoma. Pathological diagnosis of the ESD specimen revealed intramucosal gastric cancer without lymphovascular invasion (LVI). Although the surface layer of the lesion showed well and moderately differentiated tubular adenocarcinoma, clear cytoplasmic cancer cells positive for Sal-like protein-4 (SALL4) and Glypican-3 were found in a part of the deep layer. Therefore, GAED was diagnosed as present in a part of the whole lesion and covered with CDGC. Case 2 was an 83-year-old man with an elevated lesion in the gastric angulus. Biopsy revealed papillary and well-differentiated tubular adenocarcinomas. Pathological diagnosis of the ESD specimen revealed intramucosal gastric cancer without LVI. The entire lesion was occupied by papillary and tubular cancer cells, and had clear vesicles. Pure GAED was diagnosed, because the cells were SALL4 positive. In both cases, resection was curative despite the difference in pathological features.

A 70-year-old man underwent endoscopy, which revealed a slightly depressed and elevated gastric cancer with suspected submucosal invasion of the mid gastric body. Biopsy specimens revealed differentiated tubular adenocarcinoma. We also detected lung and esophageal cancer and prioritized treatment of these lesions, and the patient underwent three endoscopies to monitor changes in gastric cancer. The tumor size and color remained unchanged; however, the marginal ridge was prominent, and the depressed area was deeper on subsequent evaluation. Total gastrectomy was performed 9 months after the first endoscopy. Histopathological examination of the resected specimens showed muscularis propria invasion, well-differentiated tubular adenocarcinoma involving the superficial mucosa, and tumor cells showing clear cytoplasm and a columnar or three-dimensional structure, between the deep mucosa and submucosa. The cells were immunopositive for Sal-like protein 4 and glypican 3; therefore, the patient was diagnosed with gastric adenocarcinoma with enteroblastic differentiation (GAED). This rare gastric cancer variant constituted approximately 70% of the entire lesion, and we observed significant lymphovascular invasion and lymph node metastasis. GAED is a rare histopathological subtype of gastric cancer described in recent years. Few cases of this tumor are reported to date; therefore, our study significantly contributes to the literature.

Adenocarcinoma with enteroblastic differentiation (ACED) has high malignant potential. It is known as clear-cell adenocarcinoma, which is a special type of adenocarcinomas characterized by primitive intestine-like structures. Although ACED is often encountered in the stomach, it is very rare in the colon and has not been sufficiently reported. ACED has also not been described in the WHO and Japanese Colonic Carcinoma Classification. ACED has biological characteristics of easy metastasis and a poor prognosis than these of tubular adenocarcinoma. Therefore, all cases of colonic ACED that have been reported previously required either surgery or chemotherapy. We describe a case of flat-elevated-type and 15 mm in size colonic ACED that was successfully treated with endoscopic submucosal dissection. We report our case along with a relevant literature review.

Gastric adenocarcinoma with enteroblastic differentiation (GAED) is a very rare variant of alpha-fetoprotein-producing gastric cancer (AFPGC). GAED is histologically characterized by cuboidal or columnar cells, which resemble those found in the primitive gut and have clear cytoplasm. In previously reported cases, GAED exhibit more aggressive behavior, as well as AFPGC, than conventional gastric cancer, such as marked lymphovascular invasion, lymph node metastasis, and liver metastasis. And also GAED was usually located in a deep mucosal layer and was covered by a conventional adenocarcinoma (CA) component. Based on these findings, GAED is considered to develop from CA during the process of tumor invasion and proliferation. We present a very rare case of early-stage GAED achieved curatively resected via endoscopic submucosal dissection, in which the lesion was composed of a pure enteroblastic differentiation component without a CA component.

Gastric adenocarcinoma (GA) with enteroblastic differentiation is a subset of gastric cancer with poor prognosis. RNA-Seq data of The Cancer Genome Atlas of GA (TCGA-STAD) revealed a positive correlation between SALL4, a representative enteroblastic marker, and DNMT3A expression. Here, we conducted immunohistochemical analysis of GA to clarify the clinicopathological significance of DNMT3A expression and its correlation with enteroblastic differentiation. Of the 346 cases of solitary GA analyzed, 120 (34.7%) showed unequivocal DNMT3A nuclear expression. DNMT3A expression was associated with Lauren\'s intestinal type, papillary and tubular architectures, high frequency of lymphatic and vascular invasion, and lymph node metastasis (each, P < 0.01). Log-rank test revealed that DNMT3A-positive cases recurred more frequently with a predilection for liver metastasis (P < 0.01) and showed poorer overall and recurrence-free survival (each, P < 0.05). With respect to surrogate markers of molecular subtypes, DNMT3A-positive cases more frequently showed p53 overexpression (P < 0.001). Consistent with the results of TCGA data analysis, DNMT3A-positive cases exhibited enteroblastic morphology (18.3% vs. 0.9%, P < 0.001) and expressed enteroblastic markers, SALL4 (32.5% vs. 3.1%, P < 0.001) and glypican-3 (22.5% vs. 4.4%, P < 0.001) more frequently than did DNMT3A-negative cases. Additionally, GAs showing enteroblastic differentiation, morphologically or immunohistochemically, expressed DNMT3A with significantly higher frequency and intensity than did conventional GAs (P < 0.001). Our findings suggest DNMT3A as a potential therapeutic target for this conventional therapy-refractory cancer subtype.

Gastric adenocarcinoma with enteroblastic differentiation (GAED) is a rare variant of gastric adenocarcinoma. Clinicopathologically, GAED is known to be aggressive and is characterized by frequent vascular invasion, lymphatic invasion, and liver metastasis even in early stages. SMAD4 was identified as a frequently deleted gene in GAED by copy number variation analysis in our previous next-generation sequencing study; therefore, we examined the clinicopathological impacts of SMAD4 in 51 cases of GAEDs (early: 17, advanced: 34). We performed Sanger sequencing for SMAD4 mutations and loss of heterozygosity (LOH) analysis of the SMAD4 locus, in addition to immunohistochemistry for SMAD4, to determine its clinicopathological correlations and impacts on survival. The frequency of LOH at the SMAD4 locus was 45.1%, and it was significantly higher in GAED compared to in conventional gastric adenocarcinoma. SMAD4 mutations were not found in any case. Reduced SMAD4 expression was found in 60.8% of cases; it was significantly correlated with advanced stages and lymph node metastasis and showed trends of larger tumor size and lymphatic invasion. Reduced SMAD4 expression in metastatic lymph nodes was found in 21 of 36 cases. Survival analysis revealed that reduced SMAD4 expression significantly affected the patient\'s overall survival (OS) and recurrence-free survival (RFS), although multivariate analysis showed that only liver metastasis and lymphatic infiltration (Ly+) were independent prognostic factors for OS and RFS. The SMAD4 locus is one of the susceptibility genes in this tumor, although SMAD4 mutation was not detected. Furthermore, the inactivation of SMAD4 appeared to contribute to the aggressiveness of GAED.

Gastric adenocarcinoma with enteroblastic differentiation (GAED) is a rare variant of aggressive adenocarcinoma. We demonstrated previously that GAED is genetically characterized by frequent TP53 mutation. In this study, we aimed to further clarify the mechanism of inactivation of TP53 in GAED in the light of promoter methylation of TP53, and expression of methylation-associated proteins such as Ten-eleven translocation (TET) 1 and 5-hydroxymethylcytosine (5-hmc) in addition to ATM mutations. We analyzed 51 cases of GAED. The ATM mutation was detected in only one case. Promoter methylation of TP53 was detected in 18% and frequency of loss of heterozygosity (LOH) at TP53 locus was 37.2%. Reduced TET1 expression was found in 29 cases (56.9%) and was significantly associated with advanced stage (p = 0.01), lymph node metastasis (p = 0.04), and macroscopic type (p = 0.01). Reduced 5-hmc expression was found in 28 cases (54.9%) and was significantly associated with advanced stage (p = 0.01), gender (p = 0.01), tumor location (p = 0.03), tumor size (p = 0.01), and lymph node metastasis (p = 0.01). Among 9 cases with TP53 promoter methylation, reduced expression of TET1 was observed in 6 cases, and reduced expression of 5-hmc was observed in 5 cases. Reduced expression of both TET1 and 5-hmc was significantly associated with adverse clinical outcomes. In summary, promoter methylation of TP53 is partly involved in loss of p53 expression. Aberrant methylation by reduced TET1 and 5-hmc may be involved in the development of aggressive GAED.