(A) β2M, MHC class I and MHC class II immunohistochemical staining in 5 representative cHL patients: #1, positive for all markers (Pos); #2, decreased for all markers (Dec); #3, negative for all markers (Neg); #4, positive for β2M and MHC class I, negative for MHC class II and #5: negative for β2M and MHC class I, positive for MHC class II. Individual HRS cells are depicted with a black arrow. The white arrows indicate expression on surrounding, non-malignant inflammatory cells. Scale bar, 50 μm. (B) Heatmap representing the distribution of β2M, MHC class I (MHC-I) and MHC class II (MHC-II) expression in the 108 cHL patients. White = negative, grey = decreased, black = positive and hatched = not assessable (NA). 9p24.1 genetic alterations, light pink = polysomy, medium red = copy gain, dark red = amplification and EBV status, white = negative, blue = positive, are depicted below.