Carcinosarcoma of the stomach with alpha-fetoprotein-producing hepatoid adenocarcinoma: an unexpected combination of two rare subtypes of gastric cancer in one tumor

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.

Carcinosarcoma of the stomach: four cases that expand the morphologic spectrum of gastric cancer with a primitive phenotype

Carcinosarcoma of the stomach is a rare neoplasm characterized by the presence of both epithelial and mesenchymal malignant components. We describe four examples with a focus on the characterization of the epithelial components and the histogenetic implications for this unique tumor. All patients were men aged 40-79 years. All patients developed metastatic disease, and three of them died 4-19 months after the diagnosis. Sarcomatous elements included poorly differentiated spindle cell sarcoma without distinctive differentiation (n = 4), chondrosarcoma (n = 2), and rhabdomyosarcoma (n = 1). In two cases, the sarcomatous component was recognized only in metastatic lesions. Notably, carcinomatous components were characterized by multilineage and primitive cellular differentiation, including carcinoma with enteroblastic (n = 4), hepatoid (n = 3), yolk sac tumor-like (n = 1), trophoblastic (n = 1), and neuroendocrine (n = 1) differentiation, as well as conventional tubular adenocarcinoma (n = 4). On immunohistochemistry, all four cases showed varying degrees of positive expression of primitive phenotypic markers, including alpha-fetoprotein (AFP), glypican-3, or SALL4. All tumors showed mutant patterns of p53 staining, exhibiting either diffusely positive or completely negative staining. On the basis of these findings, at least some gastric carcinosarcomas are likely to be derived from carcinoma with a primitive phenotype, including AFP-producing adenocarcinoma. Our observations suggest that sarcomatous differentiation, as well as multilineage differentiation of epithelial components, may represent increased cellular plasticity of gastric carcinoma with a primitive phenotype.