PCA and heat map showed 3 clusters of BL. PCA (A) and heat map (B) revealed the presence of 3 distinct clusters. Cluster 1 consisted of the 5 BL with a diffuse granulomatous reaction (blue), cluster 2 had 5 EBV⁺ BL with typical starry sky pattern (orange), and cluster 3 includes 8 EBV^– BL with typical starry sky (violet), 2 cases of BL with a partial granulomatous reaction, and 3 cases of EBV⁺ BL with typical starry sky. Heat map visualizing the expression levels of immune-related genes (rows) in each BL sample (column). Upregulated or downregulated genes were selected for subsequent analysis if their expression values were found to exceed an adjusted P value cutoff of <.05, after multiple testing correction using a moderated t statistic.