A distinctive subgroup of oral EBV+ B-cell neoplasm with polymorphous features is potentially identical to EBV+ mucocutaneous ulcer.

Epstein-Barr virus-positive mucocutaneous ulcer (EBVMCU) is a newly recognized provisional entity included in mature B-cell neoplasm in the latest 2016 World Health Organization Classification. It has a self-limited growth potential with a high predilection for oral cavities and occurs in age-related or iatrogenic immunodeficiency with indolent clinical courses. However, it shares histological features with EBV-positive diffuse large B-cell lymphoma (DLBCL), and this often leads to diagnostic challenges and controversies in patients with an oral EBV-positive B-cell neoplasm. The aim of this study was to better characterize and comprehend the pathophysiology of DLBCL and EBVMCU in the oral cavity. We conducted clinicopathologic and recurrent gene mutation analysis of 49 cases (14 EBV positive, 35 EBV negative), including cases diagnosed as DLBCL or B-cell lymphoproliferative disorders with high-grade morphology in the oral cavity. All EBV-positive cases matched the criteria of EBVMCU, with significantly earlier clinical stages than the EBV-negative group (P=.0006). Besides, histological analysis showed that all EBV-positive cases presented polymorphous features, whereas 91.4% (32/35) of the EBV-negative cases showed diffuse and monotonous proliferation (P<.0001). Furthermore, EBV-positive cases presented favorable clinical outcomes without disease-related death or recurrence. Gene mutation analysis (MYD88, CD79A, CD79B, CARD11, and EZH2) revealed that 33.3% (9/27) of EBV-negative cases harbored at least 1 gene mutation, whereas no gene mutation was observed in the EBV-positive group (0/11). These results suggest that oral EBV-positive B-cell lymphoid proliferation with polymorphous features often fulfill the criteria for EBVMCU, with clinicopathologically and genetically distinctive properties.