β2M, MHC class I, and MHC class II expression in cHL patients. (A) β2M and MHC class I immunohistochemical staining in 4 representative cHL patients: #1, positive for both markers (Pos); #2, decreased for both markers (Dec); #3 and #4, negative for both markers (Neg). Individual HRS cells are depicted with a black arrow. The white arrows indicate expression on surrounding, nonmalignant inflammatory cells. Scale bar, 50 μm. (B) Heat map representing the distribution of β2M and MHC class I (MHC-I) expression in the 108 cHL patients. White, negative; gray, decreased; black, positive; hatched, not assessable (NA). Reprinted with permission from Cancer Immunology Research 2016; 4: 910.