ARAF is a serine/threonine kinase and member of the RAF family that functions as a key component of the RAS-RAF-MEK-ERK mitogen-activated protein kinase (MAPK) signaling cascade 1. This pathway controls cellular growth and proliferation, and ARAF catalyzes ATP-dependent phosphorylation events that propagate signals from receptor tyrosine kinases downstream to MEK1/2 and ERK1/2 kinases 2. Mechanistically, ARAF operates within a three-layered coherently orchestrated signaling module that directs physiological functions including cell cycle progression and survival 1. ARAF mutations drive cancer through activation of MAPK signaling. Rare but recurrent activating mutations in ARAF have been identified across diverse malignancies including lung adenocarcinoma, where variants such as S214C and S214F demonstrate functional importance for tumor formation and drug resistance 3. ARAF mutations also occur in histiocytic neoplasms and Erdheim-Chester disease, where they activate ERK signaling 45. Additionally, ARAF mutations are found in Rosai-Dorfman-Destombes disease lesions, suggesting clonal disease origins 6. Clinically, ARAF-mutant tumors respond to MEK inhibition. A clinical trial demonstrated 89% overall response rate with the MEK1/2 inhibitor cobimetinib in histiocytic neoplasms regardless of genotype, including ARAF-mutant cases 4. RAF inhibitor sensitivity varies by inhibitor class, with type I inhibitors showing equipotency across RAF isoforms, while type II inhibitors exhibit relative sparing of ARAF 2.