Primary gastric choriocarcinoma - a rare and aggressive tumor with multilineage differentiation: A case report.

Background: Primary choriocarcinoma of the stomach (PCCS) is a rare tumor, with fewer than 60 cases published in the English-language literature up to December 2018. In this paper, we present the complex immunoprofile of one PCCS and a hypothesis regarding its histogenesis.

Case Summary: A 66-year-old previously healthy male underwent an emergency palliative gastrectomy for a gastric obstructive tumor. The histologic examination and immunoprofile of tumor cells showed a mixed tumor that consisted of choriocarcinoma (90%) and moderate differentiated adenocarcinoma (10%), with hepatic metastases (Stage pT2NxM1L1V1R0) and microsatelite stable status. The patient died one month after surgery. The tumor cells showed focal positivity for CDX2 (adenocarcinoma component), HCG (choriocarcinoma) and CD138 (plasmacytoid carcinoma component) and were negative for HER-2, α-fetoprotein, VEGF, maspin and markers of epithelial-mesenchymal transition. The gastric mucosa cells displayed positivity for CDX2, Hepar A and CD138. The complex immunoprofile and literature data synthesis prove that the gastric mucosa cells can present a multilineage differentiation.

Conclusion: PCCS should be considered as an aggressive variant of microsatellite stable gastric adenocarcinoma of an epithelial type, and not a germ cell tumor.