RPS6KB1 and hairy cell leukemia: The vast majority (>90%) of HCL cases displayed cytoplasmic p-AKT, p-p70S6K and p-4E-BP1 immunoreactivity in a significant percentage of the neoplastic population in the absence of p-mTOR denoting that phosphorylation of p70S6K and 4E-BP1 is largely mediated by BRAF/ERK pathway or p-AKT.