Inclusion Criteria:

          -  Pathologically confirmed T or NK cell lymphoma at the enrolling institution. For
             CTCL, patients with stage IB disease or greater are eligible.

          -  Relapse or refractory disease after at least 1 systemic therapy

          -  Age ≥ 18

          -  ECOG ≤ 2

          -  Measurable disease defined by:

               -  Lugano Classification for systemic lymphoma or

               -  Absolute atypical lymphocytes ≥ 1000 cells/μL for diseases characterized by
                  leukemic disease

               -  mSWAT > 0 or Sezary count ≥ 1000 cells/μL for CTCL

          -  Previous systemic anti-cancer therapy must have been discontinued at least 2 weeks
             prior to treatment. Glucocorticoids aimed at controlling lymphoma-related symptoms
             are allowed as long as they are tapered down to 20mg or less by the time of
             ruxolitinib initiation. Topical steroids for CTCL are permitted.

          -  Patients must meet the following lab criteria:

               -  ANC ≥ 1.0/mm^3, platelets ≥ 100 x 10^9/L or ≥ 75 x 10^9/L (if related to
                  lymphoma), Hgb ≥ 8g/dL

               -  Total bilirubin ≤ 1.5 x upper limit of normal (ULN); ≤ 3 x ULN if due to
                  lymphoma involvement; AST and ALT ≤ 3 x ULN; ≤ 5 x ULN if due to lymphoma
                  involvement

               -  Creatinine clearance ≥ 30 mL/min

          -  For patients with positive hepatitis B core antibody or surface antigen, hepatitis B
             PCR must be negative and prophylaxis with entecavir or equivalent is required.

        Exclusion Criteria:

          -  Any serious medical condition, laboratory abnormality, or psychiatric illness that
             would prevent the subject from signing the informed consent form.

          -  Uncontrolled concurrent illness including, but not limited to, ongoing or active
             infection, uncontrolled diabetes, clinically significant pneumonitis, symptomatic
             congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or
             psychiatric illness/social situations that would limit compliance with study
             requirements.

          -  ECOG performance status >2

          -  Prior therapy with ruxolitinib

          -  Concurrent use of other anti-cancer agents or treatments.

             °Patients with more than one type of lymphoma may be enrolled after discussion with
             the MSK Principal Investigator

          -  Known history of testing positive for human immunodeficiency virus (HIV) or known
             acquired immunodeficiency syndrome (AIDS) within 12 months prior to initiating study
             treatment.

          -  Women of reproductive potential† must have a negative Serum ß human chorionic
             gonadotropin (ß-HCG) pregnancy test.

               -  A female of reproductive potential is a sexually mature female who: has not
                  undergone a hysterectomy or bilateral oophorectomy; or has not been naturally
                  postmenopausal for at least 24 consecutive months (i.e. has had menses at any
                  time in the preceding 24 consecutive months).