D. EBV-positive mucocutaneous ulcer
Histologic findings from the biopsy showed stratified squamous mucosa and respiratory-type mucosa with large areas of surface ulceration. There were dense underlying lymphoid infiltrates composed of lymphocytes, transformed lymphoid cells, and plasma cells. The transformed cells resembled atypical immunoblastic or Hodgkin and Reed-Sternberg–like cells (Figure 2A) dispersed between lymphocytes with no evidence of palisaded lymphocytes around those. These cells showed strong positivity for CD20, Pax5, MUM1, CD30, and CD15 on immunohistochemical staining (Figure 2B). More than 90% of the cells’ nuclear expression also showed EBV positivity on EBV-encoded RNA testing, but the results of B-cell clonality analysis using polymerase chain reaction were negative for any monoclonal B-cell population. No lymphoepithelial lesion, dysplasia, or epithelial malignant neoplasm was seen.