<qa>  What is the sample for CD19 expression?- The patient s malignancy will need to be assessed for CD19 expression by flow cytometry or immunohistochemistry performed at the NIH. If unstained, paraffinembedded bone marrow or lymphoma sections are available from prior biopsies, these can be used to determine CD19 expression by immunohistochemistry; otherwise, patients will need to come to the NIH for a biopsy to determine CD19 expression. The sample for CD19 expression can come from a biopsy obtained at any time before enrollment. 