Molecular and cytogenetic characterization of a new case of t(5;17)(q35;q21) variant acute promyelocytic leukemia

A novel t (5; 17) (q35; q21) associated with t (8; 21) (q22; q22) in a patient with acute myeloid leukemia: case report and review of literature

The t (8; 21) (q22; q22) with the resulting RUNX1- RUNX1T1 rearrangement is one of the most common cytogenetic abnormalities in acute myeloid leukemia (AML). It is associated with favorable prognosis. The t (5; 17) (q35; q21) is an uncommon translocation, fuses the gene for the nucleophosmin (NPM) to the retinoic acid receptor α(RARA) and was described essentially in acute promyelocytic leukemia (APL) variant. We present the case of a 19-year-old male patient who developed an AML with t (8; 21) (q22; q22) associated to t (5; 17) (q35; 21). Morphology and immunophenotype of the leukemic cells were compatible with AML. The patient received chemotherapy based on cytarabine and anthracycline without all-trans retinoic acid (ATRA) followed by allogenic stem cell transplantation in first remission. To the best of our knowledge, this is the first report of an association between a rare translocation t (5; 17) and t (8; 21) in AML. In this report, we will discuss the prognosis of this association as well as the treatment.

Atypical Rearrangements in APL-Like Acute Myeloid Leukemias: Molecular Characterization and Prognosis

Acute promyelocytic leukemia (APL) accounts for 10–15% of newly diagnosed acute myeloid leukemias (AML) and is typically caused by the fusion of promyelocytic leukemia with retinoic acid receptor α (RARA) gene. The prognosis is excellent, thanks to the all-trans retinoic acid (ATRA) and arsenic trioxide (ATO) combination therapy. A small percentage of APLs (around 2%) is caused by atypical transcripts, most of which involve RARA or other members of retinoic acid receptors (RARB or RARG). The diagnosis of these forms is difficult, and clinical management is still a challenge for the physician due to variable response rates to ATRA and ATO. Herein we review variant APL cases reported in literature, including genetic landscape, incidence of coagulopathy and differentiation syndrome, frequent causes of morbidity and mortality in these patients, sensitivity to ATRA, ATO, and chemotherapy, and outcome. We also focus on non-RAR rearrangements, complex rearrangements (involving more than two chromosomes), and NPM1-mutated AML, an entity that can, in some cases, morphologically mimic APL.

Acute Promyelocytic Leukemia Presenting With a Myeloid Sarcoma of the Spine: A Case Report and Literature Review

Myeloid sarcoma is a rare extramedullary tumor of immature myeloid cells. Certain known acute myeloid leukemia cytogenetic abnormalities, in particular t(8,21), has been associated with a higher incidence. Myeloid sarcoma, which rarely happens in acute promyelocytic leukemias, is more common in recurrent patients after the advent of all-trans retinoic acid (ATRA) and are rare in untreated acute promyelocytic leukemia. We described a case of, to our knowledge, de novo myeloid sarcoma of the spine confirmed as acute promyelocytic leukemia. Myeloid sarcoma is diagnosed by spinal tumor biopsy, and microscopic examination of a bone marrow smear and cytogenetic analysis led to a confirmed diagnosis of acute promyelocytic leukemia.

Genotypic and Phenotypic Characteristics of Acute Promyelocytic Leukemia Translocation Variants

Acute promyelocytic leukemia (APL) is a special disease entity of acute myeloid leukemia (AML). The clinical use of all-trans retinoic acid (ATRA) has transformed APL into the most curable form of AML. The majority of APL cases are characterized by the fusion gene PML-RARA. Although the PML-RARA fusion gene can be detected in almost all APL cases, translocation variants of APL have been reported. To date, this is the most comprehensive review of these translocations, discussing 15 different variants. Reviewed genes involved in APL variants include: ZBTB16, NPM, NuMA, STAT5b, PRKAR1A, FIP1L1, BCOR, NABP1, TBLR1, GTF2I, IRF2BP2, FNDC3B, ADAMDTS17, STAT3, and TFG. The genotypic and phenotypic features of APL translocations are summarized. All reported studies were either case reports or case series indicating the rarity of these entities and limiting the ability to drive conclusions regarding their characteristics. However, reported variants have shown variable clinical and morphological features, with diverse responsiveness to ATRA.

PLZF-RARα, NPM1-RARα, and Other Acute Promyelocytic Leukemia Variants: The PETHEMA Registry Experience and Systematic Literature Review

It has been suggested that 1–2% of acute promyelocytic leukemia (APL) patients present variant rearrangements of retinoic acid receptor alpha (RARα) fusion gene, with the promyelocytic leukaemia zinc finger (PLZF)/RAR_α being the most frequent. Resistance to all-trans-retinoic acid (ATRA) and arsenic trioxide (ATO) has been suggested in PLZF/RAR_α and other variant APLs. Herein, we analyze the incidence, characteristics, and outcomes of variant APLs reported to the multinational PETHEMA (Programa para el Tratamiento de Hemopatias Malignas) registry, and we perform a systematic review in order to shed light on strategies to improve management of these extremely rare diseases. Of 2895 patients with genetically confirmed APL in the PETHEMA registry, 11 had variant APL (0.4%) (9 PLZF-RAR_α and 2 NPM1-RAR_α), 9 were men, with median age of 44.6 years (3 months to 76 years), median leucocytes (WBC) 16.8 × 10⁹/L, and frequent coagulopathy. Eight patients were treated with ATRA plus chemotherapy-based regimens, and 3 with chemotherapy-based. As compared to previous reports, complete remission and survival was slightly better in our cohort, with 73% complete remission (CR) and 73% survival despite a high relapse rate (43%). After analyzing our series and performing a comprehensive and critical review of the literature, strong recommendations on appropriate management of variant APL are not possible due to the low number and heterogeneity of patients reported so far.

Classic and Variants APLs, as Viewed from a Therapy Response

Most acute promyelocytic leukemia (APL) are caused by PML-RARA, a translocation-driven fusion oncoprotein discovered three decades ago. Over the years, several other types of rare X-RARA fusions have been described, while recently, oncogenic fusion proteins involving other retinoic acid receptors (RARB or RARG) have been associated to very rare cases of acute promyelocytic leukemia. PML-RARA driven pathogenesis and the molecular basis for therapy response have been the focus of many studies, which have now converged into an integrated physio-pathological model. The latter is well supported by clinical and molecular studies on patients, making APL one of the rare hematological disorder cured by targeted therapies. Here we review recent data on APL-like diseases not driven by the PML-RARA fusion and discuss these in view of current understanding of "classic" APL pathogenesis and therapy response.

Acute Promyelocytic Leukemia: A Constellation of Molecular Events around a Single PML-RARA Fusion Gene

Although acute promyelocytic leukemia (APL) is one of the most characterized forms of acute myeloid leukemia (AML), the molecular mechanisms involved in the development and progression of this disease are still a matter of study. APL is defined by the PML-RARA rearrangement as a consequence of the translocation t(15;17)(q24;q21). However, this abnormality alone is not able to trigger the whole leukemic phenotype and secondary cooperating events might contribute to APL pathogenesis. Additional somatic mutations are known to occur recurrently in several genes, such as FLT3, WT1, NRAS and KRAS, whereas mutations in other common AML genes are rarely detected, resulting in a different molecular profile compared to other AML subtypes. How this mutational spectrum, including point mutations in the PML-RARA fusion gene, could contribute to the 10%–15% of relapsed or resistant APL patients is still unknown. Moreover, due to the uncertain impact of additional mutations on prognosis, the identification of the APL-specific genetic lesion is still the only method recommended in the routine evaluation/screening at diagnosis and for minimal residual disease (MRD) assessment. However, the gene expression profile of genes, such as ID1, BAALC, ERG, and KMT2E, once combined with the molecular events, might improve future prognostic models, allowing us to predict clinical outcomes and to categorize APL patients in different risk subsets, as recently reported. In this review, we will focus on the molecular characterization of APL patients at diagnosis, relapse and resistance, in both children and adults. We will also describe different standardized molecular approaches to study MRD, including those recently developed. Finally, we will discuss how novel molecular findings can improve the management of this disease.

A new transcriptional variant and small azurophilic granules in an acute promyelocytic leukemia case with NPM1/RARA fusion gene

We report here the first case of NPM1/RARA-positive acute promyelocytic leukemia (APL) preceded by myeloid sarcoma (MS) in the vertebra. A 52-year-old man was diagnosed with MS, as the tumor cells were positive for myeloperoxidase and CD68 but negative for CD163. After treatment with steroids and radiation, the size of the tumor was markedly reduced and peripheral blood count was normal. Bone marrow examination showed 89.2% consisted of unclassified promyelocytes characterized by round nuclei and abundant small azurophilic granules but no Auer rods. The results of chromosome analysis showed 46,XY,t(5;17)(q35;q12). Reverse-transcription polymerase chain reaction amplified the NPM1/RARA fusion transcripts derived from a combination of NPM1 exon 4 and RARA exon 5, or of NPM1 exon 1 and RARA exon 5; the latter of these has not been reported previously. Electron microscopic examination of the promyelocyte nuclei showed they were oval with mild nuclear chromatin condensation and small- to medium-sized nucleoli. Hematological and molecular complete remission was attained after induction therapy including all-trans retinoic acid. As MS was also diagnosed in two of the seven other reported cases of APL with NPM1/RARA, MS may occur more frequently in APL with NPM1/RARA than APL with PML/RARA.

Acute Myeloid Leukemia With Recurrent Cytogenetic Abnormalities

OBJECTIVES

Session 1 of the 2013 Society for Hematopathology/European Association for Hematopathology Workshop was devoted to the cases of acute myeloid leukemia (AML) with recurrent cytogenetic abnormalities.

METHODS

Based on World Health Organization 2008 criteria, seven specific translocations are defined as "recurrent" in AML. Of these seven, three are considered to be AML defining regardless of blast percentage. Workshop cases provided the opportunity to consider potential new AML-defining cytogenetic mutations, as well as other unique aspects of AML with cytogenetic abnormalities.

RESULTS

Most of the 38 cases submitted were acute promyelocytic leukemia (APL) with t(15;17)(q24.1;q21.1) and so-called variants (12 cases), AML with t(8;21)(q22;q22) (seven cases), AML with inv(3)(q11q26.2) (six cases), and AML with 11q23 translocations (five cases).

CONCLUSIONS

This review focuses on providing updated recommendations for the rapid diagnosis of APL, discussing the types and significance of variant RARA mutations in APL-like leukemias, and refining low-blast-count (oligoblastic) AML. In addition, the significance of unique morphologic, immunophenotypic, and genetic variations in AML defined by a recurrent cytogenetic abnormality is included.

Myeloid sarcoma: clinico-pathologic, phenotypic and cytogenetic analysis of 92 adult patients

Myeloid sarcoma (MS) is a rare neoplasm whose knowledge is largely based on case reports and/or technically dated contributions. Ninety-two MSs in adulthood with clinical data available were evaluated both morphologically and immunohistochemically. Seventy-four cases were also studied by fluorescent in situ hybridization on tissue sections and/or conventional karyotyping on bone marrow or peripheral blood. Histologically, 50% of the tumors were of the blastic type, 43.5% either monoblastic or myelomonocytic and 6.5% corresponded to different histotypes. CD68/KP1 was the most commonly expressed marker (100%), followed by myeloperoxidase (83.6%), CD117 (80.4%), CD99 (54.3%), CD68/PG-M1 (51%), CD34 (43.4%), terminal-deoxy-nucleotidyl-transferase (31.5%), CD56 (13%), CD61/linker for activation of T cells (2.2%), CD30 (2.2%) and CD4 (1.1%). Foci of plasmacytoid monocyte differentiation were observed in intestinal cases carrying inv16. Chromosomal aberrations were detected in about 54% of cases: monosomy 7(10.8%), trisomy 8(10.4%) and mixed lineage leukemia-splitting (8.5%) were the commonest abnormalities, whereas t(8;21) was rare (2.2%). The behavior was dramatic irrespective of presentation, age, sex, phenotype and cytogenetics. Most if not all, long survivors received bone-marrow transplantation. The present report expands the spectrum of our knowledge showing that MS has frequent monoblastic/myelomonocytic differentiation, displays distinctive phenotypic profile, carries chromosomal aberrations other than t(8;21), and requires supra-maximal therapy.