Immunohistochemical staining for H4K20me3 and H3K9me3. (A and B) Specimens of breast tumor were stained using anti-H4K20me3 (A) and anti-H3K9me3 (B) mAbs. Representative cases of noncancerous (a) and cancerous regions (b, c, d) are shown. Staining of cancerous regions was assessed using a three-point scoring system based on the percentage of positively stained cells. Bar, 20 μm. (C) H4K20me3 staining of tumor and nontumorigenic region. Within each specimen, the tumor region included cancerous and noncancerous regions. A high level of H4K20me3 staining in noncancerous regions (arrow) in comparison with the surrounding malignant cells (arrowhead) was observed. The lower panels were acquired at higher magnification. Bar, 50 μm. H & E, hematoxylin and eosin staining; mAbs, monoclonal antibodies.