Interestingly, these lymphomas might express epithelial and endothelial markers such EMA and CD31, posing some problems in differential diagnosis with poorly differentiated solid tumors.10 Recently, an immunohistochemistry stain for PRDM1/BLIMP1 and XBP1 have been proposed to identify PBL, however this finding remains investigational.11 This evidence concerns the gene XBP1 and lymphoma.