Janus kinases are intracellular tyrosine kinases that have recently been proven to have a crucial role in the pathogenesis and progression of several dermatological and malignant diseases.<h4>Objective</h4>The aim of this study was to investigate the immunohistochemical expression of Janus Kinase-1 (JAK1) and Janus Kinase-3 (JAK3) in the skin of mycosis fungoides .<h4>Methods</h4>The current study included 46 patients with early-stage MF, and 7 patients with late-stage MF, and 53 control samples. The gene discussed is JAK1; the disease is mycosis fungoides.