This trial tests if ruxolitinib can shrink tumors in patients with a specific type of leukemia called T-cell large granular lymphocyte leukemia. Ruxolitinib works by blocking enzymes that cancer cells need to grow. The goal is to see if this medication can help these patients when other treatments might not work. Ruxolitinib is an oral medication used to treat myelofibrosis and polycythemia vera, but its effects in these conditions are uncertain.