• To assess the safety and tolerability of imatinib in patients with T NHL [ Time Frame: 3 years ] [ Designated as safety issue: Yes ]
• To assess the duration of response in patients with T NHL treated with imatinib [ Time Frame: 3 years ] [ Designated as safety issue: No ]
• To assess the progression free survival and overall survival of T NHL patients treated with imatinib [ Time Frame: 3 years ] [ Designated as safety issue: No ]

The purpose of this research study is to evaluate the overall response rate to imatinib mesylate in participants with relapsed or refractory T cell non-Hodgkin's lymphoma. This drug has been used in chronic myeloid leukemia and information from those other research studies suggests that it may help to treat T cell non-Hodgkin's lymphoma.

• Participants will take the study drug orally each day of each eight week treatment cycle.
• During all treatment cycles, participants will have a physical exam and will be asked questions about their general health and specific questions about any problems they might be having and any medications they may be taking.
• If the participant has skin lesion, photographs will be taken of the skin lesion to assess the response of the tumor to study treatment. CT scans will be used to follow the participants response to treatment.
• Blood tests, including chemistry, hematology, and other tests to measure any additional effect of the study drug and disease status will also be performed.

Inclusion Criteria:

• Histologically confirmed T NHL, excluding T prolymphocytic leukemia, T lymphoblastic lymphoma, and T/NK large granular lymphocytic leukemia.
• Measurable disease, defined as at least one bidimensionally measurable site of disease measuring at least 1.5cm in greatest diameter.
• Failed at least one systemic chemotherapy or biologic therapy for T cell lymphoma unless it can be clearly documented that the patient can not tolerate such therapy.
• 18 years of age or older
• Life expectancy of greater than 3 months
• ECOG Performance Status of lesser then or equal to 2
• Normal organ and marrow function as outlined in the protocol
• Agree to the use of adequate contraception prior to study entry and for the duration of the study

Exclusion Criteria:

• Chemotherapy or radiotherapy within 4 weeks prior to entering the study
• Receiving any other study agents
• CNS lymphoma requiring active therapy
• History of allergic reactions attributed to compounds of similar chemical or biologic composition to imatinib mesylate
• Participants requiring concomitant administration of any medications or substances that are inhibitors or inducers of CYP3A4 are ineligible
• Patient previously received radiotherapy to 25% or greater of the bone marrow
• Uncontrolled intercurrent illness including but not limited to ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that would limit compliance with study requirements
• Pregnant or lactating women
• History of a different malignancy except for individuals who have been disease-free for at least 5 years and are deemed by the investigator to be at low risk for recurrence of that malignancy
• HIV-positive individuals on combination antiretroviral therapy
• Known chronic liver disease
• Major surgery within 2 weeks prior to study entry

• Brigham and Women's Hospital
• Novartis