An extremely rare case of Epstein-Barr virus-associated gastric carcinoma with differentiation to neuroendocrine carcinoma

Epstein-Barr virus (EBV)-associated gastric carcinoma (EBVGC) is defined as a neoplasm comprising monoclonal proliferation of EBV-infected gastric epithelial cells. Although the typical histology is gastric carcinoma with lymphoid stroma (GCLS), the histologic features of the tumor vary. We report herein the case of a 78-year-old man with multiple simultaneous EBVGCs revealing different histopathologic morphologies; one was mixed adenoneuroendocrine carcinoma (MANEC), and the other was GCLS. Both tumor types exhibited positive results for EBV in situ hybridization. To the best of our knowledge, this represents the first report of EBVGC showing neuroendocrine differentiation. Immunohistochemistry also revealed a loss of gastrointestinal features, including CDX2, MUC5AC, and MUC6 expression, among tumor cells from the neuroendocrine component of the MANEC. We describe the pathologic features of this rare neoplasm and discuss the mechanisms underlying the neuroendocrine differentiation of EBVGC cells, along with providing a brief review of the literature.