PRIMARY OBJECTIVE:~I. To evaluate overall response rate of leflunomide treatment.~SECONDARY OBJECTIVES:~I. To assess complete response rate and duration of response of leflunomide treatment.~II. To assess toxicities of leflunomide treatment. III. To assess disease status by the CAILS (composite assessment of index lesion severity).~EXPLORATORY OBJECTIVE:~I. To generate a preliminary ribonucleic acid (RNA) signature associated with response of CD30+ lymphoproliferative disorders (LYPDs) cells to leflunomide.~OUTLINE:~Patients receive leflunomide orally (PO) once daily (QD) on days 1-28. Treatment repeats every 28 days for up to 13 cycles in the absence of disease progression or unacceptable toxicity.~After completion of study treatment, patients are followed up every 3 months for 12 months.
This trial studies how well leflunomide works for the treatment of patients with CD30+ lymphoproliferative disorders that have come back (relapsed) or do not respond to treatment (refractory). Leflunomide may stop the growth of cancer cells by blocking some of the enzymes needed for cell growth.