Cutaneous T cell lymphomas (CTCLs) are hematopoietic malignancies derived from skin-homing CD4 T cells and have been increasing in incidence over the last 30 years.  This group of diseases include localized malignancies that are restricted to small patches of skin, which carry a favorable prognosis, as well as leukemic forms of the disease, including Sézary syndrome, that exhibit malignant circulating cells.  Despite a growing number of targeted therapies in lymphoma becoming available and being assessed for efficacy in CTCL and Sézary syndrome, there are currently no validated biomarkers that can be used to predict treatment response or guide therapeutic choice.  Efficacy of systemic treatments in leukemic CTCL and Sézary syndrome remains poor; these forms of the disease are often refractory to multiple, serial treatments and carry a five year median survival of less than 20%.  Our efforts in the lab are to identify the genetic and molecular perturbations among the different forms of CTCL in order to better match patients with the treatment course that will be most effective.