Histogenesis of hepatoid adenocarcinoma of the stomach: molecular evidence of identical origin with coexistent tubular adenocarcinoma

Exploration of molecular markers related to chemotherapy efficacy of hepatoid adenocarcinoma of the stomach

PURPOSE

Preoperative neoadjuvant chemotherapy may not improve the prognosis of patients with hepatoid adenocarcinoma of the stomach (HAS), a rare pathological type of gastric cancer. Thus, the study aimed at the genomic and transcriptomic impacts of preoperative chemotherapy on HAS.

METHODS

Patients with HAS who underwent surgical resection at Peking University Cancer Hospital were retrospectively included in this study. Whole exome sequencing and transcriptome sequencing were performed on pre-chemotherapy, non-chemotherapy and post-chemotherapy samples. We then compared the alterations in molecular markers between the post-chemotherapy and non-chemotherapy groups, and between the chemotherapy-effective and chemotherapy-ineffective groups, respectively.

RESULTS

A total of 79 tumor samples from 72 patients were collected. Compared to the non-chemotherapy group, the mutation frequencies of several genes were changed after chemotherapy, including TP53. In addition, there was a significant increase in the frequency of frameshift mutations and cytosine transversion to adenine (C > A), appearance of COSMIC signature 6 and 14, and a reduced gene copy number amplification. Interestingly, the same phenomenon was observed in chemotherapy-ineffective patients. In addition, many HAS patients had ERBB2, FGFR2, MET and HGF gene amplification. Moreover, the expression of immune-related genes, especially those related to lymphocyte activation, was down-regulated after chemotherapy.

CONCLUSION

Chemotherapy is closely associated with changes in the molecular characteristics of HAS. After chemotherapy, at genomic and transcriptome level, many features were altered. These changes may be molecular markers of poor chemotherapeutic efficacy and play an important role in chemoresistance in HAS. In addition, ERBB2, FGFR2, MET and HGF gene amplification may be potential therapeutic targets for HAS.

Hepatoid adenocarcinoma of the stomach with neuroendocrine differentiation: A case report and review of literature

BACKGROUND

Both hepatoid adenocarcinoma of the stomach (HAS) and neuroendocrine differentiation (NED) are rare histological subtypes of gastric cancer with unique clinicopathological features and unfavorable outcomes. HAS with NED is even rarer.

CASE SUMMARY

Here, we report a 61-year-old man with HAS with NED, as detected by gastric wall thickening by positron emission tomography/computed tomography for a pulmonary nodule. Distal gastrectomy was performed, and pathological examination led to the diagnosis of HAS with NED. However, liver metastases occurred 6 mo later despite adjuvant chemotherapy, and the patient died 27 mo postoperatively.

CONCLUSION

We treated a patient with HAS with NED who underwent adjuvant chemotherapy after radical surgery and still developed liver metastases. We first report the detailed processes of the treatment and development of HAS with NED, providing an important reference for the clinical diagnosis and treatment of this condition.

Hepatoid adenocarcinoma of the stomach with neuroendocrine differentiation: A case report and review of literature

BACKGROUND

Both hepatoid adenocarcinoma of the stomach (HAS) and neuroendocrine differentiation (NED) are rare histological subtypes of gastric cancer with unique clinicopathological features and unfavorable outcomes. HAS with NED is even rarer.

CASE SUMMARY

Here, we report a 61-year-old man with HAS with NED, as detected by gastric wall thickening by positron emission tomography/computed tomography for a pulmonary nodule. Distal gastrectomy was performed, and pathological examination led to the diagnosis of HAS with NED. However, liver metastases occurred 6 mo later despite adjuvant chemotherapy, and the patient died 27 mo postoperatively.

CONCLUSION

We treated a patient with HAS with NED who underwent adjuvant chemotherapy after radical surgery and still developed liver metastases. We first report the detailed processes of the treatment and development of HAS with NED, providing an important reference for the clinical diagnosis and treatment of this condition.

Hepatoid adenocarcinoma-Clinicopathological features and molecular characteristics

Hepatoid adenocarcinoma (HAC) is a rare, malignant, extrahepatic tumor with histologic features similar to those of hepatocellular carcinoma. HAC is most often associated with elevated alpha-fetoprotein (AFP). HAC can occur in multiple organs, including the stomach, esophagus, colon, pancreas, lungs, and ovaries. HAC differs greatly from typical adenocarcinoma in terms of its biological aggression, poor prognosis, and clinicopathological characteristics. However, the mechanisms underlying its development and invasive metastasis remain unclear. The purpose of this review was to summarize the clinicopathological features, molecular traits, and molecular mechanisms driving the malignant phenotype of HAC, in order to support the clinical diagnosis and treatment of HAC.

Combined tubular adenocarcinoma, neuroendocrine carcinoma and adenocarcinoma with enteroblastic differentiation arising in Barrett esophagus

Adenocarcinoma (AC) with neuroendocrine carcinoma (NEC) or enteroblastic (ENT) differentiation rarely develops in Barrett's esophagus (BE). A 76-year-old man was diagnosed with Barrett's AC (cT1bN0M0) and underwent thoracoscopic esophagectomy. A type 0-IIc + 0-Is lesion measuring 26 × 21 mm was macroscopically observed on a background of long segment BE (pT1bN0M0). The tumor comprised three different histological types of carcinoma (NEC, AC with ENT differentiation and moderately differentiated AC). NEC showed positivity for synaptophysin, chromogranin A and insulinoma-associated protein 1 with a Ki-67 index of 60.6%. ENT tumors were immunopositive for AFP and sal-like protein 4, and focally immunopositive for human chorionic gonadotrophin. The amounts of NEC, ENT and AC were 40%, 40% and 20%, respectively. p53 expression was positive throughout the tumor. Rb expression was negative at the NEC, but positive at the ENT and AC. CD4 and CD8 densities were lower in the NEC segment than in the AC and ENT segments, and PD-L1 expression was negative throughout the tumor. Early cancer arising in BE with a combination of tubular AC, ENT tumors and NEC is very rare. Our observations might contribute to understanding the carcinogenetic pathways and tumor microenvironment of NEC and ENT tumors.

Early hepatoid adenocarcinoma of the stomach with signet ring cell carcinoma: A case report and clinicopathological features

Background

Hepatoid adenocarcinoma of the stomach (HAS) is a rare subtype of gastric cancer with poor prognosis, and its clinicopathological features are not well understood, so the pathology from the clinical biopsy is easily misdiagnosed, especially for special or atypical HAS. We present an extremely rare early HAS with signet ring cell carcinoma and evaluate its clinicopathological features.

Case presentation

A 51-year-old female patient of Chinese Han ethnicity with upper abdominal pain for 5 years and worsened abdominal pain for 1 month was admitted to our hospital. Esophagogastroduodenoscopy showed a submucosal tumor-like elevated lesion with central depression in the greater curvature of the junction between the antrum and body. Histopathological examination from the biopsy revealed medium-low-differentiation adenocarcinoma with signet ring cell carcinoma. Radical gastrectomy was performed, and the final diagnosis was early HAS with signet ring cell carcinoma.

Conclusions

HAS with signet ring cell carcinoma is a special type of HAS and extremely rare. It is first presented for this extremely rare type of HAS, which contributes to strengthen the understanding for the clinicopathological characteristics of HAS and especially promote early detection of HAS.

Integrative analysis reveals a clinicogenomic landscape associated with liver metastasis and poor prognosis in hepatoid adenocarcinoma of the stomach

Hepatoid adenocarcinoma of the stomach (HAS) is a rare subtype of gastric cancer (GC) that histologically resembles hepatocellular carcinoma (HCC). Despite its low incidence, HAS had a poor 5-year survival rate. Currently, the linkages between clinicopathological and genomic features of HAS and its therapeutic targets remain largely unknown. Herein, we enrolled 90 HAS patients and 270 stage-matched non-HAS patients from our institution for comparing clinicopathological features. We found that HAS had worse overall survival and were more prone to develop liver metastasis than non-HAS in our cohort, which was validated via meta-analysis. By comparing whole-exome sequencing data of HAS (n=30), non-HAS (n=63), and HCC (n=355, The Cancer Genome Atlas), we identified a genomic landscape associated with unfavorable clinical features in HAS, which contained frequent somatic mutations and widespread copy number variations. Notably, signaling pathways regulating pluripotency of stem cells affected by frequent genomic alterations might contribute to liver metastasis and poor prognosis in HAS patients. Furthermore, HAS developed abundant multiclonal architecture associated with liver metastasis. Encouragingly, target analysis suggested that HAS patients might potentially benefit from anti-ERBB2 or anti-PD-1 therapy. Taken together, this study systematically demonstrated a high risk of liver metastasis and poor prognosis in HAS, provided a clinicogenomic landscape underlying these unfavorable clinical features, and identified potential therapeutic targets, laying the foundations for developing precise diagnosis and therapy in this rare but lethal disease.

Comprehensive Analysis of Genomic Alterations in Hepatoid Adenocarcinoma of the Stomach and Identification of Clinically Actionable Alterations

Simple Summary

Hepatoid adenocarcinoma of the stomach (HAS) is a subset of gastric cancer (GC) histologically characterized by hepatocellular carcinoma-like foci with or without alpha-fetoprotein secretion, which is easily misdiagnosed. Genomic alterations and potential targets for this population are still largely unknown. Additionally, treatment regimens of HAS are mainly based on GC guidelines, which is not reasonable for diseases with great heterogeneity. The present study comprehensively depicts the genomic features of HAS, and they are significantly different from GC, AFP-producing GC (AFPGC), and liver hepatocellular carcinoma (LIHC). Multiple aggressive behavior-related amplificated or deleted regions in HAS are firstly reported. Moreover, reliable and practicable clinically actionable alterations for HAS are identified, providing evidence for making personalized therapy based on the genomic characteristics of HAS instead of GC.

Abstract

Hepatoid adenocarcinoma of the stomach (HAS) is a rare malignancy with aggressive biological behavior. This study aimed to compare the genetic landscape of HAS with liver hepatocellular carcinoma (LIHC), gastric cancer (GC), and AFP-producing GC (AFPGC) and identify clinically actionable alterations. Thirty-eight cases of HAS were collected for whole-exome sequencing. Significantly mutated genes were identified. TP53 was the most frequently mutated gene (66%). Hypoxia, TNF-α/NFκB, mitotic spindle assembly, DNA repair, and p53 signaling pathways mutated frequently. Mutagenesis mechanisms in HAS were associated with spontaneous or enzymatic deamination of 5-methylcytosine to thymine and defective homologous recombination-related DNA damage repair. However, LIHC was characteristic of exposure to aflatoxin and aristolochic acid. The copy number variants (CNVs) in HAS was significantly different compared to LIHC, GC, and AFPGC. Aggressive behavior-related CNVs were identified, including local vascular invasion, advanced stages, and adverse prognosis. In 55.26% of HAS patients there existed at least one clinically actionable alteration, including ERBB2, FGFR1, CDK4, EGFR, MET, and MDM2 amplifications and BRCA1/2 mutations. MDM2 amplification with functional TP53 was detected in 5% of HAS patients, which was proved sensitive to MDM2 inhibitors. A total of 10.53% of HAS patients harbored TMB > 10 muts/Mb. These findings improve our understanding of the genomic features of HAS and provide potential therapeutic targets.

Case Report: A Rare Case of Hepatoid Adenocarcinoma in Stomach and Duodenum Simultaneously

HAC is a rare extrahepatic malignancy histologically resembling hepatocellular carcinoma which can occur in many organs. Especially for cases carrying HAC within the stomach or duodenum, we found that typically HAC only happened in either of them and there was no case exhibiting HAC in both sites. Here, we presented a case having HAC in both sites and to our knowledge, this is the first report presenting HAC in these two distinct organs simultaneously. Firstly, a 57-year-old male was tested for increased serum alpha-fetoprotein level. Following PET-CT images showed strengthened FDG uptake in the gastric antrum and proximal duodenum. Esophagogastroduodenoscopy also revealed an irregular lump at the gastric antrum and a deep ulceration at the duodenum bulb. Next, an immunohistochemistry panel confirmed the diagnosis of HAC. Finally, genetic tests were performed on this patient after the clinical diagnosis of HAC to reveal the molecular etiology.

Effect of immune checkpoint inhibitors in patients with gastric hepatoid adenocarcinoma: a case report and literature review

Gastric hepatoid adenocarcinoma (GHAC) is a highly aggressive histological subtype of gastric cancer (GC) with similar tissue morphology to hepatocellular carcinoma. GHAC frequently produces alpha-fetoprotein (AFP) and has a poor prognosis; however, standardized treatment remains elusive. We report a male patient in his early 60s with GHAC who received immunotherapy, and the curative effect was evaluated. He was admitted because of progressive fatigue and dizziness for 2 months. He had experienced spontaneous epigastric pain with muscular defense of the epigastrium and accompanying tenderness 1 year earlier and underwent radical gastrectomy. Immunohistochemistry showed that hepatocyte-specific marker (Hep) was highly-expressed, indicating probable GHAC. Additionally, imaging suggested GC recurrence or gastric stump cancer. Radioimmunoassay indicated an AFP level of >1210.00 µg/L, and liver biopsy was performed following abdominal contrast-enhanced computed tomography. Pathology showed a few hepatocytes and proliferative fibrous connective tissue. The patient received three cycles of chemotherapy, with no obvious improvement. The possibility of surgical treatment was excluded, and immunotherapy or palliative treatment was selected. He received 11 cycles of a programed death-1 (PD-1) monoclonal antibody, and the effect of treatment was satisfactory. The mechanism of action of immunotherapy in GHAC warrants further investigation.

The Value of Perioperative Chemotherapy for Patients With Hepatoid Adenocarcinoma of the Stomach Undergoing Radical Gastrectomy

BACKGROUND

Hepatoid adenocarcinoma of the stomach (HAS) is a rare type of gastric cancer, but the role of perioperative chemotherapy is still poorly understood. The aim of this retrospective study was to investigate the associations between perioperative chemotherapy and prognosis of HAS.

METHOD

We retrospectively analyzed patients with locally advanced HAS who received radical surgery in Peking University Cancer Hospital between November 2009 and October 2020. Patients were divided into neoadjuvant chemotherapy-first (NAC-first) group and surgery-first group. The relationships between perioperative chemotherapy and prognosis of HAS were analyzed using univariate, multivariate survival analyses and propensity score matching analysis (PSM).

RESULTS

A total of 100 patients were included for analysis, including 29 in the NAC-first group and 71 in the surgery-first group. The Her-2 amplification in HAS patients was 22.89% (19/83). For NAC-first group, 4 patients were diagnosed as tumor recession grade 1 (TRG1), 4 patients as TRG 2, and 19 patients as TRG 3. No significant difference in prognosis between the surgery-first group and the NAC-first group (P=0.108) was found using PSM analysis. In the surgery-first group, we found that the survival rate was better in group of ≥6 cycles of adjuvant chemotherapy than that of <6 cycles (P=0.013).

CONCLUSION

NAC based on platinum and fluorouracil may not improve the Overall survival (OS) and Disease-free survival time (DFS) of patients with locally advanced HAS. Patients who received ≥6 cycles of adjuvant chemotherapy had better survival. Therefore, the combination treatment of radical gastrectomy and sufficient adjuvant chemotherapy is recommended for patients with locally advanced HAS.

Hepatoid esophagogastric adenocarcinoma and tumoral heterogeneity: a case report

Hepatoid adenocarcinoma of the stomach is an uncommon subtype of gastric cancer remarkably similar to hepatocellular carcinoma in histopathological analysis. It is also commonly associated with high serum alfa-fetoprotein and a poorer prognosis, despite the emergence of new therapeutic options. In recent years, next generation sequencing (NGS) technology has made it possible to identify and describe the genes and molecular alterations common to gastric cancer thereby contributing to the advancement of targeted therapies. A 62-year-old patient, with no prior risk factor for hepatocellular carcinoma (HCC), presented to the emergency room with dysphagia for solids, abdominal pain and weight loss of about 3 kilograms over 3 months. Histopathological analysis presented with disparities regarding HER2 and programmed death-ligand 1 (PD-L1) status in the primary and metastatic sites. We describe a case of a de novo metastatic, human epidermal growth factor receptor 2 (HER2) positive esophagogastric junction hepatoid adenocarcinoma. Although this is a rare subgroup of gastric cancer, treatment strategies were based in recent studies in immunotherapy and guided therapy, taking into consideration the molecular findings from the patient's tumor NGS analysis. Data about HER2 and PDL1 heterogeneity were also reviewed. Despite the aggressiveness and rarity of this histology, the patient had a good response to treatment.

Hepatoid Adenocarcinoma of the Stomach: Current Perspectives and New Developments

Hepatoid adenocarcinoma of the stomach (HAS) is a rare malignant tumor, accounting for only 0.17-15% of gastric cancers. Patients are often diagnosed at an advanced disease stage, and their symptoms are similar to conventional gastric cancer (CGC) without specific clinical manifestation. Morphologically, HAC has identical morphology and immunophenotype compared to hepatocellular carcinoma (HCC). This is considered to be an underestimation in diagnosis due to its rare incidence, and no consensus is reached regarding therapy. HAS generally presents with more aggressive behavior and worse prognosis than CGC. The present review summarizes the current literature and relevant knowledge to elaborate on the epidemic, potential mechanisms, clinical manifestations, diagnosis, management, and prognosis to help clinicians accurately diagnose and treat this malignant tumor.

Integrated clinicopathological and immunohistochemical analysis of gastric adenocarcinoma with hepatoid differentiation: an exploration of histogenesis, molecular characteristics, and prognostic markers

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.

Effect of Immune Checkpoint Inhibitors Plus Chemotherapy on Advanced Gastric Cancer Patients with Elevated Serum AFP or Hepatoid Adenocarcinoma

PURPOSE

Alpha-fetoprotein-producing gastric cancer (AFPGC) and hepatoid adenocarcinoma of stomach (HAS) are rare types of gastric cancer, with specific clinical manifestations and poor prognosis. The standardized treatment process of such cancers remains elusive. We aim to investigate the efficacy of immunotherapy combined with chemotherapy on patients with AFPGC or HAS.

PATIENTS AND METHODS

AFPGC and HAS patients who underwent immunotherapy and/or chemotherapy as the first-line treatment at our institute from June 2016 to December 2018 were enrolled in this observational study. Their clinicopathological characteristics, serum AFP level and treatment methods were collected. The progression-free survival (PFS) and overall survival (OS) were analyzed and compared between patients who received immunotherapy plus chemotherapy and those received chemotherapy.

RESULTS

A total of 21 patients with advanced AFPGC or HAS were included in the study and the median follow-up time was 28.0 months. Of the 21 patients, 7 patients received immunotherapy of PD-1 antibody (nivolumab) plus chemotherapy and 14 patients as control received chemotherapy with or without Herceptin/Apatinib. The median progression-free survival (mPFS) time was 5.0 months (4.3 months in the control group and 22.0 months in the immunotherapy group). The median overall survival (mOS) time of the control group was 16.0 months (14.0 months in chemotherapy alone subgroup, 20.0 months in chemotherapy plus Apatinib or Herceptin subgroup), while the mOS of patients receiving immunotherapy was not reached.

CONCLUSION

This study suggested PD-1 checkpoint inhibitor plus chemotherapy could benefit AFPGC and HAS patients. Its mechanism of action warrants further investigation.

The prognosis of hepatoid adenocarcinoma of the stomach: a propensity score-based analysis

BACKGROUND

To investigate whether there is a distinct difference in prognosis between hepatoid adenocarcinoma of the stomach (HAS) and non-hepatoid adenocarcinoma of the stomach (non-HAS) and whether HAS can benefit from radical surgery.

METHODS

We retrospectively reviewed 722 patients with non-HAS and 75 patients with HAS who underwent radical gastrectomy between 3 November 2009 and 17 December 2018. Propensity score matching (PSM) analysis was used to eliminate the bias among the patients in our study. The relationships between gastric cancer type and overall survival (OS) were evaluated by the Kaplan-Meier method and Cox regression.

RESULTS

Our data demonstrate that there was no statistically significant difference in the OS between HAS and non-HAS {K-M, P = log rank (Mantel-Cox), (before PSM P = 0.397); (1:1 PSM P = 0.345); (1:2 PSM P = 0.195)}. Moreover, there were no significant differences in the 1-, 2-, or 3-year survival rates between patients with non-HAS and patients with HAS (before propensity matching, after 1:1 propensity matching, and after 1:2 propensity matching).

CONCLUSION

HAS was generally considered to be an aggressive gastric neoplasm, but its prognosis may not be as unsatisfactory as previously believed.

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

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.

Establishment and characterization of the GC-030-35 cell line derived from gastric hepatoid adenocarcinoma

Purpose

Gastric hepatoid adenocarcinoma is a rare subtype of primary gastric cancer and is a high-grade form of malignancy. However, the pathogenesis and molecular biology of gastric hepatoid adenocarcinoma remain poorly understood. The aim of this study was to establish and characterize a new human gastric hepatoid adenocarcinoma cell line, GC-030-35.

Materials and methods

The GC-030-35 cell line was established from tumor cells from a 58-year-old Chinese man with gastric hepatoid adenocarcinoma. The cultured cells underwent immunocytochemistry and flow cytometry to confirm the tumor cell phenotype. RNA sequencing was performed to analyze the differences in gene expression between GC-030-35 cells compared with normal gastric epithelial cells. A zebrafish assay was performed. Gene enrichment analysis and interrogation of the bioinformatics databases, the Gene Ontology (GO) database and the Kyoto Encyclopedia of Genes and Genomes (KEGG) database, were used for pathway analysis.

Results

Flow cytometry analysis of the GC-030-35 cells showed a positive expression rate for CD44+ of 10.7%, high cell clonality, an average plating efficiency of 32%, cell-doubling time of 29.2 hours, and cell proliferation for >15 generations in serial culture. The zebrafish assay showed the ability of the GC-030-35 cells to proliferate, promote angiogenesis, and metastasize. RNA sequencing identified the functional clustering of 6,601 differentially expressed genes of GC-030-35, which were significantly different when compared with nonneoplastic gastric epithelial cells. Pathway enrichment analysis and interrogation of the GO and KEGG bioinformatics databases identified genes for microbial metabolism in diverse environments (63 genes), metabolism of xenobiotics by cytochrome P450 (CYP450; 25 genes), and the drug metabolism cytochrome P450 (28 genes).

Conclusion

A human gastric hepatoid adenocarcinoma cell line, GC-030-35, was developed and characterized by comparison with normal gastric epithelial cells. Bioinformatics and gene analysis data showed that the CYP450 gene was significantly differentially expressed by GC-030-35 cells.

Hepatoid adenocarcinoma of the stomach: a unique subgroup with distinct clinicopathological and molecular features

OBJECTIVES

Hepatoid adenocarcinoma of the stomach (HAS) is characterized by histological resemblance to hepatocellular carcinoma and a poor prognosis. The aim of this study is to elucidate the clinicopathological and molecular characteristics of HAS.

METHODS

Forty-two patients with HAS who received gastrectomy were enrolled in this study. Based on a panel of 483 cancer-related genes, targeted sequencing of 24 HAS and 22 clinical parameter-matched common gastric cancer (CGC) samples was performed. Prognostic factors for overall survival (OS) and disease-free survival (DFS) were analysed with the Kaplan-Meier method.

RESULTS

The most frequently mutated gene in both HAS and CGC was TP53, with a mutation rate of 30%. Additionally, CEBPA, RPTOR, WISP3, MARK1, and CD3EAP were identified as genes with high-frequency mutations in HAS (10-20%). Copy number gains (CNGs) at 20q11.21-13.12 occurred frequently in HAS, nearly 50% of HAS tumours harboured at least one gene with a CNG at 20q11.21-13.12. This CNG tended to be related to more adverse biobehaviour, including poorer differentiation, greater vascular and nerve invasion, and greater liver metastasis. Pathway enrichment analysis revealed that the HIF-1 signalling pathway and signalling pathways regulating stem cell pluripotency were specifically enriched in HAS. The survival analysis showed that a preoperative serum AFP level ≥ 500 ng/ml was significantly associated with poorer OS (p = 0.007) and tended to be associated with poorer DFS (p = 0.05).

CONCLUSION

CNGs at 20q11.21-13.12 happened frequently in HAS and tended to be related to more adverse biobehaviour. The preoperative serum AFP level was a sensitive prognostic biomarker for DFS and OS.

Next-generation sequencing analysis for gastric adenocarcinoma with enteroblastic differentiation: emphasis on the relationship with hepatoid adenocarcinoma

Histologically tubulopapillary structures with glycogen-rich clear cytoplasm in gastric adenocarcinoma with enteroblastic differentiation (GAED) are well known, but a solid growth pattern can also be observed as a minor component. In contrast, hepatoid adenocarcinoma (HAC) of the stomach shows many overlapping features, including solid pattern and α-fetoprotein expression. In this study, we employed next-generation sequencing (NGS) to establish a molecular/clinicopathological concept of GAED and clarify whether these two tumors should be grouped together in one category. Among 2273 primary gastric cancers treated in our hospital between 2008 and 2017, we defined 51 cases as GAEDs showing tubulopapillary or solid patterns that express at least one of the following markers: α-fetoprotein, glypican-3, or spalt-like transcription factor 4. All cases previously diagnosed as HAC in our hospital had clear cytoplasm and were included as GAEDs by histological re-evaluation and immunohistochemical findings. We performed NGS for 24 histologically typical GAEDs and Sanger sequencing for the remaining cases. The most frequently mutated gene was TP53, and almost all cases with missense mutation showed p53 overexpression. An analysis of copy number variation revealed that ERBB2 amplification was the most frequent in GAED. Additionally, HER2 immunohistochemistry and fluorescence in situ hybridization confirmed that 22% of informative cases were HER2 positive. There was no correlation between molecular/clinicopathological parameters and α-fetoprotein expression or growth patterns in GAED. Our analysis showed that GAED frequently harbors TP53 mutations and ERBB2 amplification. As with conventional gastric adenocarcinoma, trastuzumab may be effective for GAED. Furthermore, HAC may be subcategorized as a solid-type GAED.

HER2 is frequently overexpressed in hepatoid adenocarcinoma and gastric carcinoma with enteroblastic differentiation: a comparison of 35 cases to 334 gastric carcinomas of other histological types

AIMS

α-Fetoprotein (AFP)-producing gastric carcinoma (AFPGC) is one of the most aggressive GC subtypes. Frequent expression of human epidermal growth factor receptor 2 (HER2) has previously been reported in hepatoid adenocarcinoma (HAC), a major histological subtype of AFPGC originating from common-type GC (CGC). However, HER2 expression levels in other AFPGC histological subtypes are unknown. In this study, we analysed HER2 expression in GCs with primitive phenotypes in addition to HAC.

METHODS

HER2 expression was evaluated in representative complete sections from 16 HACs, 19 GCs with enteroblastic differentiation (GCEDs) and 334 GCs of other histological types as controls. The Ruschoff/Hofmann method was used to score HER2 immunohistochemistry. Samples with a HER2 score of 2+ were further assessed using fluorescence in situ hybridisation. Oncofetal protein (OFP) expression in HAC and GCED was tested via immunohistochemical staining for AFP, glypican 3 and Sal-like protein 4.

RESULTS

Thirty of 35 HAC/GCED cases comprised more than two histological patterns. The HER2 positivity rates of each histological component in the HACs/GCEDs were 25.0% for HAC (n=16), 34.6% for GCED (n=26) and 48.1% for CGC (n=27), which were higher than those of the control group (13.8%). Additionally, the majority of CGC components in HACs/GCEDs were positive for OFP (88.9%).

CONCLUSIONS

HER2 is frequently overexpressed not only in HAC but also in GCED and CGC components of HACs/GCEDs, which suggests an association between HER2 and OFP expression. Moreover, our findings suggest that HER2-positive CGC has a higher risk of progression to HAC/GCED than HER2-negative GC.

Gastric Adenocarcinoma with Dual Differentiation toward Neuroendocrine and α-Fetoprotein-Producing Features: Report of 2 Cases

Some gastric carcinomas show composite features of neuroendocrine carcinoma (NEC) and α-fetoprotein (AFP)-producing carcinoma, which are very rare; only a few cases have been reported to date. We reviewed an additional 2 such cases of gastric carcinoma, which were both advanced aggressive tumors showing regional lymph node metastasis and distant metastasis. Both cases were accompanied by ordinary adenocarcinoma forms, implying that they had preceded the NEC and AFP-producing carcinoma components. A distinctive feature was the finding suggestive of dual differentiation of tumor cells to neuroendocrine and AFP-producing phenotypes, which was identified even in the metastatic tumor in the regional lymph node. Because both tumors predominantly showed poorly differentiated forms, the final pathologic diagnosis must rely on the immunohistochemistry. Pathologists should always keep in mind the existence of such tumors for the correct diagnosis of some gastric carcinomas with specific phenotypes, especially in pathologic diagnosis on biopsy.

Alpha-Fetoprotein-Producing Extrahepatic Tumor: Clinical and Histopathological Significance of a Case

INTRODUCTION

The serum rise of alpha-fetoprotein (AFP) has been relationed to hepatic tumors. Other than these, such as gastric adenocarcinoma, can present with high levels of this glycoprotein. One rare kind of gastric adenocarcinoma, called hepatoid subtype, has two essential features: hepatoid differentiation in histology and high levels of AFP in serum.

DISCUSSIONS

We report a Spanish female who consulted because of fatigue, anorexia, and weight loss. In laboratory data, she presented anemia and markedly elevation of AFP. On CT scan, a gastric mass resulted without hepatic dissemination, and subsequently, gastroduodenoscopy was performed for histological diagnosis. Then, an ulcerated mass was detected and sample was taken, resulting in poorly-differentiated adenocarcinoma of stomach with hepatoid tissue foci, with intense positivity for AFP-immunohistochemical staining. This rare cancer has poor prognosis even with early gastrectomy and chemotherapy.

A case of adenocarcinoma with enteroblastic differentiation of the ampulla of Vater

Cancer of the ampulla of Vater is rare, though it has various histological types and its histogenesis is fascinating in view of the anatomically complex nature of the ampulla. Fetal gut-like adenocarcinoma, usually found in the stomach, can also develop in the ampullary region in extremely rare cases. Here we present a case of ampullary adenocarcinoma with enteroblastic and neuroendocrine differentiation. A 55-year-old woman presented with an epigastric pain. Endoscopic examination revealed a 2-cm submucosal tumor-like lesion in the ampulla. The surgical specimen showed that an exposed protruding type of tumor appeared as a well-demarcated whitish-yellow solid mass. Microscopically, the tumor had proliferated in the common channel and invaded the duodenal submucosa with mucosal lesion of intestinal-type adenocarcinoma. The main tumor consisted of three different histological types showing transitional areas: adenocarcinoma with enteroblastic differentiation (ENT), neuroendocrine carcinoma (NEC), and well differentiated adenocarcinoma (WEL). Morphologically the ENT resembled fetal gut and immunohistochemically expressed SALL4 and glypican 3. The WEL was positive for CK20 and CDX2, revealing an intestinal-type phenotype. AFP and HepPar1 were not evident in any part of the lesion. We speculated this tumor had arisen from intestinal-type adenocarcinoma of the common channel and acquired enteroblastic and neuroendocrine differentiation during growth.

Clinicopathologic and immunohistochemical characteristics of gastric adenocarcinoma with enteroblastic differentiation: a study of 29 cases

BACKGROUND

Gastric adenocarcinoma with enteroblastic differentiation (GAED) has been recognized as a variant of alpha-fetoprotein (AFP)-producing gastric carcinoma, although its clinicopathologic and immunohistochemical features have not been fully elucidated.

METHODS

To elucidate the clinicopathologic and immunohistochemical features of GAED, we analyzed 29 cases of GAED, including ten early and 19 advanced lesions, and compared these cases with 100 cases of conventional gastric adenocarcinoma (CGA). Immunohistochemistry for AFP, glypican 3, SALL4, and p53 was performed, and the phenotypic expression of the tumors was evaluated by immunostaining with antibodies against MUC5AC, MUC6, MUC2, CD10, and caudal-type homeobox 2 (CDX2).

RESULTS

Lymphatic and venous invasion was more frequent in GAED (76 and 72 %) than in CGA (41 and 31 %; P ≤ 0.001). Lymph node metastasis was more frequently observed in GAED (69 %) than in CGA (38 %; P = 0.005), as were synchronous or metachronous liver metastases (GAED, 31 %; CGA, 6 %; P ≤ 0.001). Immunohistochemically, all GAED were positive for at least one of three enteroblastic linage markers (AFP, glypican 3, and SALL4). Glypican 3 was the most sensitive marker (83 %) for GAED, followed by SALL4 (72 %) and AFP (45 %), whereas no CGA was positive. Furthermore, the rate of positive p53 staining was 59 % in GAED. Regarding the mucin phenotype, CD10 and CDX2 were diffusely or focally expressed in all GAED cases. Invasive areas with hepatoid or enteroblastic differentiation were negative for CD10 and CDX2.

CONCLUSIONS

Clinicopathologic features of GAED differ from those of CGA. GAED shows aggressive biological behavior, and is characteristically immunoreactive to AFP, glypican 3, or SALL4.

One case of hepatoid adenocarcinoma, a rare subtype of gastric cancer

Here we report a rare but important special type of gastric cancer, hepatoid adenocarcinoma. Hepatoid adenocarcinoma of the stomach (HAS) is typically associated with clinicopathological presentations mimicking hepatocellular carcinoma (HCC) such as elevated alpha-fetoprotein (AFP) in serum. The incidence of HAS is extremely low, and it is easily misdiagnosed/missed based on a pathological analysis. This disease is usually diagnosed at advanced stage, and it tends to develop liver metastases and have a poor prognosis.

Hepatoid Adenocarcinoma of the Gall Bladder-A Rare Variant

Hepatoid adenocarcinoma is a rare variant of extra hepatic adenocarcinoma, consisting of foci of both adenomatous and hepatocellular differentiation with morphological and functional resemblance to hepatocellular carcinoma and hence correct diagnosis is a challenge. The most frequent site is stomach. We present this case of hepatoid carcinoma of the gallbladder for its rarity and difficulty in diagnosis which on histology showed papillae, sheets and trabaculae of polygonal cells with eosinophilic cytoplasm and vesicular nuclei with prominent nucleoli with adjacent foci showing high grade dysplasia.

Hepatoid adenocarcinoma of the stomach: A case report and literature review

Hepatoid adenocarcinoma (HAC) is a rare form of gastric cancer that has unique clinicopathological features and an extremely poor prognosis. The present case report describes a patient who was referred to the No. 461 Hospital of PLA (Changchun, China) due to nausea and occasional vomiting of acid/water. The patient was diagnosed with gastric signet-ring cell carcinoma and surgery was recommended. A total gastrectomy was performed on the operable lesion. Histopathological analysis revealed that the tumors exhibited two pathological changes: HAC and signet-ring cell carcinoma differentiation. Furthermore, the tumor cells were immunohistochemically positive for α-fetoprotein, cytokeratin low/high molecular weight, Cam5.2, cytokeratin 7, p53, epithelial membrane antigen and carcinoembryonic antigen. Previous studies and our experience have suggested that HAC is an aggressive type of adenocarcinoma; however, radical surgery and chemotherapy may positively impact clinical outcomes.

AFP-producing hepatoid adenocarcinoma of appendix: a case report of 18F-FDG PET/CT

Hepatoid adenocarcinoma (HAC) is a rare tumor. We described here a rare case of appendix HAC. A 59-year-old man underwent F-18-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) for gradually elevated alpha-Fetoprotein level. Multiple masses in the abdominal cavity with moderate FDG uptake were revealed, suggesting malignant tumor with peritoneal metastasis. The patient underwent radical resection, and the postoperative pathological result was HAC originated from the appendix. To our knowledge, it is the first report of HAC of the appendix. Our study suggests that FDG PET/CT may help in detecting the primary tumor and the metastases of HAC.

Gastric composite tumor of alpha fetoprotein-producing carcinoma/hepatoid adenocarcinoma and endocrine carcinoma with reference to cellular phenotypes

Alpha-fetoprotein-producing carcinoma (AFPC)/hepatoid adenocarcinoma (HAC) and neuroendocrine carcinoma (NEC) are uncommon in the stomach. Composite tumors consisting of these carcinomas and their histologic phenotypes are not well known. Between 2002 and 2007, to estimate the prevalence of composite tumors consisting of tubular adenocarcinoma, AFPC/HAC and NEC, we reviewed specimens obtained from 294 consecutive patients treated surgically for gastric cancer. We examined histological phenotype of tumors of AFPC or NEC containing the composite tumor by evaluating immunohistochemical expressions of MUC2, MUC5AC, MUC6, CDX2, and SOX2. Immunohistochemically, AFPC/HAC dominantly showed the intestinal or mixed phenotype, and NEC frequently showed the gastric phenotype. In the composite tumor, the tubular and hepatoid components showed the gastric phenotype, and the neuroendocrine component showed the mixed type. The unique composite tumor predominantly showed the gastric phenotype, and the hepatoid and neuroendocrine components were considered to be differentiated from the tubular component.

Histologic and immunohistochemical analyses of α-fetoprotein--producing cancer of the stomach

BACKGROUND AND AIM

As the histogenesis and development of α-fetoprotein-producing gastric cancer (AFPGC) have not yet been elucidated, we analyzed the histologic and immunologic relationship between the histologic type of the mucosal lesion considered to be the primary lesion, and that of its invasive lesion, in 36 cases of AFPGC.

PATIENTS AND METHODS

We reviewed 23 AFPGCs with mucosal lesions (1 mucosal and 22 submucosal or deeper invasive tumors) among 36 AFPGCs that had been resected endoscopically or surgically between 1970 and 2005. AFPGC was defined as a tumor showing immunohistochemical positivity for either α-fetoprotein (AFP) or glypican-3. Histologic types were divided into hepatoid (HPT), enteroblastic (ENT), yolk sac tumor, and common (COM) adenocarcinoma type. The tumor phenotypes were classified into gastric, gastrointestinal, and intestinal types on the basis of immunohistochemical analysis.

RESULTS

Among the histologic types of mucosal lesions, the COM and ENT mixed type was observed in 65.2% of cases (15/23 patients), COM alone in 26.1% (6/23), and ENT alone in 8.7% (2/23) of cases. Among the invasive lesions, 16 cases (72.7%) were HPT. Both AFP and glypican-3 were positive in 60.9% (14/23) of mucosal lesions and in 90.9% (20/22) of invasive lesions. With regard to phenotypic expression, 82.6% (19/23) of mucosal lesions were the intestinal type, compared with 95.5% (21/22) of invasive lesions.

CONCLUSIONS

These findings suggest that many cases of AFPGC develop as COM or ENT in the mucosa, which differentiate into ENT and HPT during the process of tumor invasion and proliferation, acquiring AFP production ability.

Combined tubular adenocarcinoma and hepatoid adenocarcinoma arising in Barrett esophagus

Hepatoid adenocarcinoma arising in the esophagus is extremely rare. To date, there are only 3 cases in the world English literature. We report the fourth case here. A 76-year-old Japanese man was admitted to our hospital because of the deterioration of nephritic syndrome. He presented with chest burn, and the endoscopic examination of upper digestive tract disclosed the tumor in the lower esophagus. The subtotal esophagectomy was undertaken because of esophageal cancer. The postoperative histologic examination showed the finding of combined tubular adenocarcinoma and hepatoid adenocarcinoma arising in Barrett esophagus. Immunohistochemically, hepatoid adenocarcinoma cells were positive for a-fetoprotein, hepatocyte, a1-antitrypsin, a1-antichymotrypsin, and CDX2, but negative for MUC5AC and MUC6. Esophageal hepatoid adenocarcinoma seems to be closely associated with Barrett esophagus and show the intestinal phenotype rather than gastric phenotype.

Long-term results of gastrectomy for alpha-fetoprotein-producing gastric cancer

BACKGROUND

alpha-Fetoprotein (AFP)-producing gastric cancer is a rare tumour. It is said to have a high incidence of liver metastasis and poor prognosis. This study sought to evaluate long-term outcomes in such patients.

METHODS

Records of consecutive patients with gastric carcinoma who underwent preoperative measurement of serum AFP levels and gastrectomy were reviewed to identify those who satisfied the following criteria: preoperative AFP level exceeding 40 ng/ml with a decrease after gastrectomy, or raised preoperative AFP level (10-39 ng/ml) and resected tumour showing histologically characteristic features or immunohistochemically positive AFP production.

RESULTS

Of 3374 patients with gastric cancer, 53 (1.6 per cent) met the selection criteria. Tumours were characterized by a high incidence of nodal (79 per cent) or liver (53 per cent) metastasis. Preoperative serum AFP levels showed no correlation with tumour size, depth of invasion, disease stage or survival. The 5-year survival rate was 34 per cent. Five patients survived after recurrence following multimodal treatment. A rising AFP level during follow-up always led to tumour recurrence, but the level remained normal in 11 of 31 patients with recurrence.

CONCLUSION

AFP-producing tumours represent a small subgroup of gastric cancer with high metastatic potential. Postoperative serum AFP level can help predict recurrence but a normal level does not mean absence of recurrence. Prognosis is not as poor as previously thought, and multimodal treatment may be worthwhile even in patients with recurrent tumour.

SALL4 represents fetal gut differentiation of gastric cancer, and is diagnostically useful in distinguishing hepatoid gastric carcinoma from hepatocellular carcinoma

The novel stem cell marker SALL4 has been identified as a diagnostic marker of germ cell tumors, especially yolk sac tumors, in gonadal organs. To clarify the significance of SALL4 as an oncofetal protein, we investigated SALL4 expression by immunohistochemistry in non-neoplastic stomach and gastric carcinoma with particular emphasis on á-fetoprotein (AFP)-producing gastric carcinoma, as AFP-producing gastric carcinoma shares expression of AFP and glypican 3 (GPC3) with yolk sac tumors and hepatic neoplasms. A total of 338 gastric carcinomas, 60 hepatocellular carcinomas, and 48 cholangiocellular carcinomas were studied by immunohistochemistry on tissue microarrays. In addition, more detailed whole tissue section immunohistochemistry was performed on non-neoplastic gastric tissue from 5 adult and 8 fetal specimens, 6 hepatoblastomas, and 31 cases of AFP-producing gastric carcinomas. SALL4 expression was observed in the neofetal stomach in gestational week 9 and disappeared thereafter. It was also identified by tissue microarray study in a fraction of gastric carcinomas (51 of 338, 15%), associated with older age (P=0.0001), male sex (P=0.0033), intestinal-type histology (P=0.0001), and synchronous liver metastasis (P=0.0047). AFP and GPC3 were closely associated with SALL4 expression in gastric carcinoma (both, P<0.0001), and a full-section study indicated that SALL4 was positive in all 31 cases of AFP-producing gastric carcinoma with diffuse staining in 24 cases (78%). Diffuse SALL4 expression was observed in the histologic patterns of hepatoid (89%), glandular (57%), and clear cell (39%) AFP-producing gastric carcinoma. In addition, SALL4 expression was completely negative in hepatoblastoma (n=6) and hepatocellular carcinoma (n=60). SALL4 is an oncofetal protein similar to AFP and GPC3, but it represents fetal gut differentiation in gastric carcinoma. SALL4 is a sensitive marker for AFP-producing gastric carcinoma and is especially useful to distinguish hepatoid gastric carcinoma from hepatocellular carcinoma.

Hepatoid adenocarcinoma of the stomach: histogenesis and progression in association with intestinal phenotype

Hepatoid adenocarcinoma is an extrahepatic tumor characterized by morphological similarities to hepatocellular carcinoma. The lesions contain a tubular adenocarcinoma that seems to develop "hepatoid" features, but the relation between the tubular adenocarcinomatous and the hepatoid components remains unclear. We compared the cellular phenotypes of 23 cases of hepatoid adenocarcinoma of the stomach having tubular adenocarcinomatous components with 69 cases of non-hepatoid adenocarcinoma of the stomach. Afterward, we examined the expression of CDX2 and p53 in the tubular adenocarcinomatous and hepatoid components of hepatoid adenocarcinoma. Both components of hepatoid adenocarcinoma were classified into 4 phenotypic categories according to the immunohistochemical results for CD10, MUC2, MUC5AC, and MUC6. The complete intestinal phenotype (CD10+, MUC5AC-, MUC6-) was most frequently observed in the adenocarcinomatous and hepatoid components (61% and 65%, respectively). In contrast, no gastric phenotype (MUC5AC+, MUC6+, MUC2-, CD10-) was observed in any of the hepatoid adenocarcinoma components. The positivity for p53 protein in the adenocarcinomatous and hepatoid components was concordant. The expression of CDX2 with early differentiation and maintenance of intestinal epithelial cells was observed in all of the adenocarcinomatous components, whereas 9 of the 23 hepatoid components (39%) were negative for CDX2. These findings suggest that hepatoid adenocarcinoma arises from an adenocarcinoma with an intestinal phenotype and that its hepatoid component is in some way related to reduced CDX2 expression.

Diffuse hepatoid adenocarcinoma in the peritoneal cavity

Hepatoid adenocarcinoma (HAC) is a rare tumor that occurs mostly in the gastrointestinal tract. We encountered a 68-year-old man suffering from HAC with severe ascites. The serum and ascitic alpha-fetoprotein (AFP) levels were markedly high. Computed tomography (CT) revealed that multiple nodular lesions were disseminated only in the peritoneal cavity. Based on laparoscopic and histological findings, this tumor was diagnosed as diffuse HAC which was developed primarily in the peritoneum. Despite treatments with appropriate chemotherapy, he died six months after diagnosis. According to literature updates, this is the first documented case of diffuse HAC which developed in the peritoneum.

Combined small-cell carcinoma of the stomach: p53 and K-ras gene mutational analysis supports a monoclonal origin of three histological components

Primary small-cell carcinoma (SmCC) is extremely rare in stomach. We reported an autopsy case of combined gastric SmCC with p53 and K-ras mutational analysis. Histologically, the tumour was composed of well-differentiated adenocarcinoma surrounding the central dominant SmCC component with scattered nests of squamous cell carcinoma. Immunohistochemically, all the neoplastic components revealed strong expression for p53 protein. Based on these findings, we hypothesized that these histologically different components originated from a same progenitor cell that possessed p53 mutation. Using Laser-capture microdissection technique and mutational analysis, we identified the same point mutations of p53 gene (A-->G transversion in codon 239) and K-ras gene (G-->A transversion in codon 13) in all the neoplastic components, but not in the adjacent normal gastric epithelium. Our results strongly support a hypothesis that the combined SmCC of stomach in this case was of monoclonal origin.