Immunohistochemical staining for DOT1L (Fig. 1a) and H3K79 methylation (Additional file 2: Figure S1a) expression was performed on 24 normal ovarian tissues, 15 benign ovarian tumors, 7 borderline ovarian tumors, and 228 malignant ovarian tumors. This evidence concerns the gene DOT1L and ovarian benign neoplasm.