RARA and PML gene rearrangements in acute promyelocytic leukemia with complex translocations and atypical features.

The translocation t(15;17) associated with acute promyelocytic leukemia (APL) results in fusion of the retinoic acid receptor alpha (RARA) gene on chromosome 17 with the putative transcription factor gene, PML, on chromosome 15. We report three cases of APL with complex cytogenetic translocations and five cases with atypical phenotypic features with rearrangements within or adjacent to the second intron of the RARA gene. Two patients demonstrated three-way translocations involving chromosomes 3, 15, and 17, but with differing breakpoints on the short arm of chromosome 3. A third patient developed a complex karyotype at the time of third relapse, but with no change in RARA and PML gene rearrangement pattern. Three patients had normal karyotypes; however, only small numbers of cells could be analyzed. One patient's leukemic cells expressed the T-cell-associated antigen CD2 and revealed T-cell receptor beta and gamma gene rearrangements. The localization of breakpoints to the second intron of the RARA gene in cytogenetically and phenotypically atypical cases provides additional support for a requisite role of the PML/RARA fusion gene in the pathogenesis of APL.

Determination of platinum in urine, ultrafiltrate, and whole plasma by isotope dilution gas chromatography-mass spectrometry compared to electrothermal atomic absorption spectrometry.

Isotope dilution gas chromatography-mass spectrometry (GC-MS) and electrothermal atomic absorption spectrometry (EAAS) are compared for platinum (Pt) determination in urine, plasma ultrafiltrate, and plasma samples from a patient undergoing cisplatin therapy. The isotope dilution GC-MS method is based on the use of lithium bis(trifluoroethyl)dithiocarbamate as a chelating agent and enriched 192Pt as an internal standard. Pt isotope ratios were measured using a Finnigan MAT 8230 organic mass spectrometer, and Pt concentrations were calculated from different sets of isotope ratios in the molecular ion of the Pt-chelate. In the EAAS method, Pt concentrations were determined using three different approaches. These were: (i) calibration curve based on aqueous standards containing Pt in 10% HCl, (ii) standard addition, and (iii) matrix digestion followed by standard addition. Good agreement was obtained for Pt concentrations determined by GC-MS and EAAS in urine samples while there were significant differences in Pt concentrations of ultrafiltrate and whole plasma samples by the two methods. Discussion of possible reasons for these differences emphasizes the need for future critical evaluation of these methods.

Lineage alteration in precursor B cell acute lymphoblastic leukemia following T cell lymphoblastic lymphoma.

A 10-year-old girl was diagnosed with lymphoblastic lymphoma; staging evaluation revealed a large mediastinal mass and normal peripheral blood and bone marrow morphology. Tumor cell immunologic marker analysis and Southern blot gene rearrangement studies demonstrated a T-cell lineage. She achieved a complete remission following multi-agent chemotherapy; however, 19 months following initial diagnosis while on maintenance therapy, she presented with typical acute lymphoblastic leukemia (ALL). The bone marrow was replaced by lymphoblasts, though the mediastinum was normal and there was no peripheral lymphadenopathy. Repeat immunophenotypic and genotypic studies demonstrated a precursor B-cell ALL lineage without expression of the T-cell surface antigens present on the original neoplasm. Repeat genotypic analysis showed immunoglobulin heavy and light chain gene rearrangements without the T-cell receptor gamma and beta gene rearrangements noted in the original lymphoblastic lymphoma. The complete alteration of lineage in these lymphoblastic processes suggests the de novo occurrence of a second neoplasm or, alternatively, an ALL relapse from a lineage-uncommitted neoplastic lymphoid progenitor cell.