Epstein-Barr virus status drives morphological and molecular intra-tumour heterogeneity in gastric cancer: insights from a case report and literature review.

This case report describes a rare case of bi-phenotypic gastric cancer with two distinct, but clonally related, histological components. The first component, associated with Epstein-Barr virus (EBV) infection, exhibited the morphological features of gastric carcinoma with lymphoid stroma, suggesting that EBV, as an effective immunogenic factor, may trigger a prominent immune response within the tumour microenvironment. The second component, which was EBV-negative, displayed tubular/papillary morphology and features of increased biological aggressiveness, such as high-grade areas and lymphatic invasion. Immunohistochemical and molecular studies confirmed that, despite the differing morphologies and immunophenotypes, both components were clonally related, with the EBV-negative area showing more complex DNA aberrations, reminiscent of chromosomally instable (CIN) lesions. This case describes clonally related EBV-positive and -negative components within a single gastric cancer, contributing to a better understanding of EBV role in tumour heterogeneity and progression and highlights the impact of EBV loss on tumour behaviour.