KRAS and sinus histiocytosis with massive lymphadenopathy: While the cytoreductive properties of cladribine are well established in RDD, further investigation into inhibition of pro-inflammatory cytokines (TNF-a, IL-6, IL-1B) and effect on molecular targets (NRAS, KRAS, MAP2K1, ARAF) may be useful to fully understand the mechanism of response and develop future targeted therapies.