Thus, HDAC1 gene expression was up-regulated in the indolent germinal centre B-cell subtype of diffuse large B-cell lymphoma compared with the more aggressive activated B-cell and type 3 subtypes.58,59 In contrast, in solid tumours HDAC1 was correlated with more advanced stages of lung cancer60 and HDAC6 showed a directly opposite influence in breast cancer and oral squamous cell carcinoma.44,61 In our study, we found no evidence for the involvement of HDAC1 or HDAC6 in the development of more aggressive CTCL based on their expression in indolent versus aggressive CTCL subtypes. This evidence concerns the gene HDAC6 and breast carcinoma.