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Background: The authors evaluated the utility of immunofluorescence staining with an antipromyelocytic leukemia (anti-PML) antibody for patients with a suspected diagnosis of new or relapsed acute promyelocytic leukemia (APL) and correlated the findings with the results of other established diagnostic modalities., Methods: Bone marrow (BM) and/or peripheral blood (PB) smears from 349 patients in whom the diagnosis of APL was considered were assessed with the anti-PML antibody using immunofluorescence. The study group included 199 patients with confirmed APL and 150 with other conditions. The results of conventional cytogenetics, reverse transcription polymerase chain reaction (RT-PCR), and fluorescence in situ hybridization (FISH) performed on these patients were correlated with the PML results., Results: Among patients with confirmed APL, anti-PML antibody was positive in 182 of 184 BM and 32 of 33 PB smears. Conventional cytogenetics demonstrated t(15;17)(q22;q12) in 166 of 182 (91%) patients; 10 had a normal karyotype, 4 had insufficient mitoses to grow in culture, 1 was inconclusive, and 1 was 48, XX, +8, +8. Anti-PML staining was positive in 9 of 10 with a normal karyotype and in all 4 cases with insufficient mitoses. RT-PCR and FISH were positive for PML-retinoic acid receptor-alpha in 169 of 172 (98%) and 90 of 94 (96%) cases, respectively. Among the patients without APL, 148 of 150 (98.6%) were negative with anti-PML antibody. The sensitivity and specificity of the test were 98.9% and 98.7%, respectively., Conclusions: PML immunofluorescence staining is a rapid (<4 hours turnaround time) and reliable frontline diagnostic approach that can facilitate initiation of targeted therapy, particularly in clinical settings where cytogenetic and molecular testing are not readily available.

Background: The extramedullary collection of leukemic cells is an infrequent complication of myeloid leukemias, and extremely uncommon in acute promyelocytic leukemia (APL)., Methods: The case reports of two patients with APL who relapsed with extramedullary disease and a review of the literature are presented., Results: Two patients with cytogenetically and molecularly confirmed APL developed extramedullary relapse in skin and lymph nodes after prior treatment with all-trans retinoic acid. A review of the literature revealed only nine cases of APL complicated by extramedullary disease. However, only one of these previously reported patients was shown to have the cytogenetic abnormality characteristic of APL., Conclusions: To the authors' knowledge, These two patients represent the first cases of cytogenetically confirmed APL treated with all-trans retinoic acid who developed extramedullary relapse. These events, which were reported infrequently in patients treated only with cytotoxic therapy, may be more common in patients receiving all-trans retinoic acid. In view of the differentiating activity of all-trans retinoic acid, which may increase the migratory capacity of these malignant cells, it is hypothesized that this agent may predispose some patients to unusual forms of relapse.

The authors describe the functional capabilities of in vivo induced neutrophils from a patient with acute promyelocytic leukemia (French-American-British M3v) treated with differentiation therapy using all-trans-retinoic acid (45 mg.m-2.day-1). The induced neutrophils from the leukemic clone appeared in the blood 7 days after therapy. Normal neutrophils, presumably derived from nonclonal normal hematopoiesis, appeared 15 days after the initiation of therapy. The induced neutrophils were separated from normal neutrophils by density gradient centrifugation. Their origin was established by fluorescence in situ hybridization. The induced neutrophils were morphologically atypical but stained for myeloperoxidase (Sudan black B) and AS-D chloroacetate esterase and were negative for alpha-naphthyl butyrate esterase. Induced neutrophils were functionally mature, showing nitroblue tetrazolium reduction in 72% of the cells compared with 84% in the normal neutrophil fraction. Both the rate and total killing of Staphylococcus aureus (American Type Culture Collection Strain 25923) were normal in both neutrophil fractions. Random locomotion was equivalent and within the normal reference range in both fractions; however, using the under-agarose technique, induced neutrophils showed a minor chemotactic defect in response to both n-formyl-methionyl-leucyl-phenylalanine (score 292, normal 338-868) and complement-derived chemotactic factors (score 420, normal 457-1408). At autopsy, induced neutrophils infiltrated necrotic myocardial tissue, suggesting a normal response to inflammatory stimuli.

Mature and immature monocytes express the CD4 molecule similar to that expressed on lymphocytes. Since monocytes and cells of myeloid lineage are derived from a common progenitor, we studied a panel of nine myeloid leukemia cell lines for the expression of the CD4 molecule. We found that six of nine myeloid leukemia cell lines (U937, KG1-B, HL-60, THP-1, HEL 92.1.7, KMOE) expressed CD4, the exceptions being the erythroleukemia line K562, myeloblast line KG1-REV, and megakaryocytic line, CHRF-288. SDS-PAGE analysis of HL-60 cells immunoprecipitated with OKT4 showed the presence of a 55 kd molecule similar in weight to that seen on lymphocytes. These data suggest that some myeloid progenitor cells express the CD4 molecule and that the CD4 may have a broader distribution within hematopoietic cells.

A 29-year-old woman developed acute promyelocytic leukemia during pregnancy. At diagnosis, immediately postpartum, she was found to have IgG kappa immunoglobulin on the surface of the leukemic cells as well as a monoclonal protein of IgG kappa specificity in her serum. These resolved with chemotherapy which induced a complete remission. Immunoglobulin gene rearrangement was not found in the leukemic cells, thus indicating that the blasts were not secreting the monoclonal protein. The authors believe that the patient had an autoantibody directed at myeloid cells which was amplified by the development of the leukemic process.