Dasatinib in Relapsed or Refractory Non-Hodgkin's Lymphoma

Primary: * To determine the Maximum Tolerated Dose (MTD) of Dasatinib in relapsed or refractory Non-Hodgkin's lymphoma (NHL) patients and to determine the safety of Dasatinib in NHL Secondary Objective: * To assess the complete and overall response rates for all Phase I and Phase II patients and to assay the levels of kinase activity in NHL specimens and correlate this activity to patient outcomes. * To determine overall survival and event free survival for all Phase I and Phase II patients. Treatment Plan This study has two phases of treatment, Phase I and Phase II. The Phase I portion of the trial will consist of a dose escalation plan with 3-6 patients being enrolled into each dose cohort. The doses of Dasatinib used in Phase I are 100 mg, 150 mg, and 200 mg. The dose that is found to be tolerated the best and also has the best treatment results will be used for Phase II. An additional 29 patients will be enrolled into Phase II. All patients will receive Dasatinib in this study. Dasatinib will be administered orally (by mouth) once daily for 28 day cycles. A cycle will be considered 28 days. Dosing will be continuous with no interruptions, unless instructed to interrupt treatment by the treating physician. The patient will be restaged after every 2 cycles of therapy, every even cycle. Therapy may continue as long as there are no clinical signs of NHL progressing and the patient is tolerating the treatment with no side effects related to the therapy. If the patient is removed from study for any reason, he/she will be followed for survival until death.