Inclusion Criteria:

- Must understand and voluntarily sign the informed consent

- Aged 20 years or older (at the time of signing the informed consent)

- Have a documented diagnosis of either: acute-, lymphoma-, or unfavorable chronic-type
adult T-cell leukemia-lymphoma

- Have received ≥1 prior anti-adult T-cell leukemia-lymphoma therapy, have achieved
stable disease or better on their immediately prior therapy and have relapsed or
progressed at the time of obtaining signed informed consent

- Subjects for whom at least 1 measurable lesion (Measurable lesion of computed
tomography scan, peripheral blood or skin lesion) is confirmed in the lesion
assessment before registration

- Have an Eastern Cooperative Oncology Group performance status of 0 to 2 at
registration

- Must be able to adhere to the study visit schedule and other protocol requirements

- Must agree to comply to Lenalidomide Pregnancy Prevention Risk Management Plan

Exclusion Criteria:

- Have a history of central nervous system involvement or present with central nervous
system symptoms, and are diagnosed with central nervous system lymphoma by
cerebrospinal fluid cytology examination, head computed tomography scan or brain
magnetic resonance imaging during the screening

- Are pregnant or lactating

- Any condition including the presence of laboratory abnormalities, which places the
subject at unacceptable risk if he/she were to participate in the study. Examples of
such medical condition are, but are not limited to, as follows:

- Uncontrolled diabetes mellitus as defined by the investigator or
sub-investigator

- Chronic congestive heart failure (New York Heart Association Class III or IV)

- Unstable angina pectoris, angioplasty, stenting, or myocardial infarction
(within 6 months before starting the study drug)

- Clinically significant cardiac arrhythmia that is symptomatic or requires
treatment, or asymptomatic sustained ventricular tachycardia (subjects with
controlled atrial fibrillation that is asymptomatic are eligible for this study)

- Major surgery within 28 days of the start of study treatment

- Exhibit grade 4 neurological disorders

- Patients who are at a high risk for a thromboembolic event and are not willing to
take venous thromboembolic prophylaxis.

- Develop active tuberculous disease, herpes simplex, systemic mycosis, or other active
infections requiring systemic administration of antibiotics, antiviral agents, or
antifungal drugs

- Known human immunodeficiency virus positivity

- Have hepatitis B surface antigen-positive, or hepatitis C virus anti-body positive.
In case hepatitis B core antibody and/or hepatitis B surface antibody is positive
even if hepatitis B surface antigen-negative, a hepatitis B virus deoxyribonucleic
acid test should be performed and if positive the subject will be excluded

- Any significant medical condition, laboratory abnormality, or psychiatric illness
that would prevent the subject from participating in the study

- Have a history of allogenic stem cell transplantation

- Have received autologous stem cell transplantation within 12 weeks (84 days) of the
start of study treatment

- Have previously used lenalidomide

- Have a history of desquamating (blistering) rash while taking thalidomide

- Have received any investigational drugs (unapproved drugs in Japan) within 4 weeks
(28 days) of the start of study medication

- Have received any antibody agents within 12 weeks (84 days) of the start of study
medication

- Have received chemotherapeutic agents or immunomodulatory drugs for the treatment of
adult T-cell leukemia-lymphoma within 4 weeks (28 days) of the start of study
treatment

- Have received radiotherapy within 4 weeks (28 days) of the start of study treatment

- Have a history or complication of another malignant tumor other than adult T-cell
leukemia-lymphoma and the following malignant tumors, unless the patients have been
free of the disease for 5 years or longer

- Basal cell carcinoma of the skin

- Squamous cell carcinoma of the skin

- Cervical carcinoma in situ

- Carcinoma in situ of the breast

- An incidental histological finding of prostate carcinoma (TNM stage T1a or T1b)

- Early-stage gastric cancer treated with endoscopic mucosal resection or
endoscopic submucosal dissection

- Have had any of the following abnormal measurements at screening performed within 1
week (7 days) prior to the registration;

- Neutrophil count: < 1,200/µL

- Platelet count: < 75,000/µL

- Serum aspartate aminotransferase/glutamyl oxaloacetic transaminase or alanine
aminotransferase/glutamyl pyruvic transaminase: > 3 times the upper limit of
normal

- Bilirubin level: > 1.5 times the upper limit of normal

- Creatinine clearance: < 60 mL/min

- Any condition that confounds the ability to interpret data from the study.