Tetraploid acute promyelocytic leukemia with large bizarre blast cell morphology

Relapsed Acute Promyelocytic Leukemia Lacks "Classic" Leukemic Promyelocyte Morphology and Can Create Diagnostic Challenges

OBJECTIVES

Although current therapies for acute promyelocytic leukemia (APL), such as all- trans retinoic acid and arsenic trioxide, usually result in remission, some patients relapse. Early recognition of relapse is critical for prompt intervention. In this study, we systematically reviewed morphologic, immunophenotypic, and cytogenetic findings in paired diagnostic and relapsed APL cases and describe and quantify the changes in blast morphology at relapse.

METHODS

By electronic database search, we identified eight paired diagnostic and relapsed APL cases for which peripheral blood or bone marrow smears were available for review. For two cases, diagnostic material was available for relapse after hematopoietic cell transplantation.

RESULTS

Neoplastic hypergranular or microgranular promyelocytes with indented or bivalve nuclei predominated at diagnosis in all patients. Most patients had undifferentiated blasts at relapse and/or hypergranular blast equivalents with round to oval nuclei. Classic acute promyelocytic leukemia cells with bivalve nuclei and bundles of cytoplasmic Auer rods were easily identifiable in fewer than half of cases at diagnosis and rare to absent in all relapsed cases.

CONCLUSIONS

Morphologic features of relapsed APL overlap with other types of acute myeloid leukemia, creating diagnostic challenges, especially if no history is available when relapsing patients seek treatment for care.

Secondary near-tetraploidy with double der(15)t(15;17) in acute promyelocytic leukemia in relapse

Tetraploidy or near-tetraploidy is a rare cytogenetic abnormality in acute myelocytic leukemia. We report here a case of acute promyelocytic leukemia that showed near-tetraploidy with double der(15)t(15;17) the leukemia relapsed. At diagnosis, cytogenetic analysis failed to reveal any karyotypic abnormality; however, a promyelocytic leukemia-retinoic acid receptor alpha (PML/RARA) fusion transcript of the bcr3-type was detected with reverse transcriptase-polymerase chain reaction analysis, and a single PML/RARA fusion signal was observed with fluorescence in situ hybridization analysis. At the first relapse, the majority of leukemic cells showed pseudodiploid karyotypes with der(15)t(15;17), as well as additional chromosomal abnormalities, and exhibited a single PML/RARA fusion signal. A small fraction of leukemic cells, however, showed near-tetraploid karyotypes with double der(15)t(15;17), as well as some additional chromosomal abnormalities in common with the pseudodiploid clones, and exhibited double PML/RARA fusion signals. At the second and third relapses, leukemic cells with near-tetraploidy and double PML/RARA fusion signals became predominant. The PML/RARA fusion transcript of the bcr3 type was also observed at each relapse. In addition, Southern blot analysis of the RARA gene at diagnosis and at the second relapse showed a common rearranged band. Notably, giant, bizarre, and hypogranular promyelocytes expressing CD2, CD34, and HLA-DR appeared at the first relapse and became predominant at the second and third relapses. These observations indicate that the APL cells with near-tetraploidy and double der(15)t(15;17) clonally evolved from the pseudodiploid leukemic cells and exhibited the bizarre morphology and aberrant surface immunophenotypes.

Hypocellular acute promyelocytic leukemia with a tetraploid clone characterized by two t(15;17)

We describe a case of hypocellular acute promyelocytic leukemia with a tetraploid clone characterized by two t(15;17). The large leukemia cells had a bizarre nuclear configuration and multiple Auer rods. A bone marrow biopsy specimen revealed a markedly hypocellular marrow (<10% cellularity) in the absence of myelofibrosis. Myelodysplastic features were not detected. Chromosome analysis of marrow cells revealed a karyotype of 92,XXYY,del(2)(q?),t(15;17)(q22;q21)x2. Interphase fluorescence in situ hybridization revealed that the marrow cells were composed of a tetraploid clone carrying double t(15;17) and normal diploid cells. The leukemia responded well to all-trans retinoic acid. We think that the tetraploidy could be caused by endoreduplication or endomitosis of the diploid clone with single t(15;17). The unique karyotype largely contributed to the cell morphology and marrow hypoplasia, while it may not have affected on the prognosis of the acute promyelocytic leukemia.

Tetraploid acute promyelocytic leukemia with double t(15;17) and PML/RARA rearrangements detected by fluorescence in situ hybridization analysis

Acute promyelocytic leukemia (APL) is characterized by a serious hemorrhagic syndrome, unique morphologic findings, and its response to retinoids. Tetraploidy is a very rare chromosomal abnormality in acute myelocytic leukemia. This report presents a unique case of APL with a tetraploid clone characterized by two t(15;17) without other chromosomal changes, as well as PML/RARA rearrangements confirmed fluorescence in situ hybridization. The morphology of the blast cells was that of the classic M3 subtype, but the mean blast size exceeded that of control APL cases with diploidy. A chromosomal study revealed a 92,XXXX,t(15;17)(q22;q21)x2 karyotype in all 20 metaphase spreads. Despite all-trans-retinoic acid (ATRA) treatment and chemotherapy, leukemic cells persisted in the blood, and the patient died of an intracranial hemorrhage on the 16th day after admission.

Trisomy 21 and other chromosomal abnormalities in acute promyelocytic leukemia

We describe a case of acute promyelocytic leukemia (APL) with t(15;17)(q22;q12) and trisomy 21 as an additional change in a patient who died at relapse after achieving complete remission (CR) for the duration of 20 months. A survey of 42 cases of APL with cytogenetic study performed at our institutionover the past 10 years showed 12 cases (28.6%) having chromosomal changes in addition to t(15;17). Trisomy 8 and trisomy 21 as additional changes were noted in 4 and 2 cases, respectively, with one patient showing both trisomies simultaneously. Two cases showed t(15;17) in hyperdiploid clones. Among the 10 patients with follow-up data, all eventually relapsed and none achieved continuous complete remission 1. Survival analysis performed in APL patients with adequate follow-up data showed no significant difference in overall and disease free survival between those with and without additional cytogenetic changes. After excluding cases with one induction death, the overall survival was significantly in favor of the group without additional cytogenetic abnormalities (P = 0.022). Late relapses may therefore be significantly more common in APL patients with additional cytogenetic abnormalities, and may not be reflected by analysis focused at three-year survival only. As APL is now considered a curable disease, any confirmed long-term survival impact of additional cytogenetic changes is expected to have important management implications.

Atypical blasts and bone marrow necrosis associated with near-triploid relapse of acute promyelocytic leukemia after arsenic trioxide treatment

The pathologic features of acute promyelocytic leukemia (APL) with t(15;17)(q22;q21) are highly characteristic, which with few exceptions enable a firm diagnosis to be made on morphologic grounds. An APL patient in first relapse presented with large, bizarre circulating blasts and bone marrow necrosis 2 weeks after chemotherapy consolidation for an arsenic trioxide-induced remission. Although a morphologic diagnosis could not be reached, cytogenetic investigations showed a near-triploid clone with t(15;17), confirming APL in second relapse. This case showed that clonal evolution with additional karyotypic aberrations might alter the blast morphology and pathologic features in APL.