Hidden mastocytosis in acute myeloid leukemia with t(8;21)(q22;q22)

Systemic Mastocytosis with Associated Hematological Neoplasms. Diagnostic features and unique response pattern to tyrosine kinase inhibitors and allo-bone marrow transplantation therapy

Systemic Mastocytosis is a clonal proliferation of mast cells; in a significant fraction of cases it is associated with another concurrent hematological neoplasm. Molecular analysis of KIT mutations and other associated genetic alterations suggest a common origin in the stem cell compartment. Mast cell infiltration patterns in bone marrow biopsy may be subtle in cases associated with t (8;21) AML. Here we report three cases of clonally related SM-AHN, two cases with SM-CMML and one case with SM- t (8;21) AML. We describe in detail the bone marrow infiltration pattern at diagnosis and during the course of treatment with allogeneic stem cell transplant and novel TK inhibitors, showing the unique dynamics of mast cell clearance after therapy.

Comprehensive mastocytosis data analysis from a single center

Mastocytosis is a very rare disorder and is divided into three prognostically distinct variants by World Health Organization: Cutaneous mastocytosis (CM), systemic mastocytosis (SM), and mast cell sarcoma or localized mast cell (MC) tumors. The wide range of complaints may cause patients to consult various clinics, with resulting mis- or underdiagnosis. Therefore, cooperation between different subspecialties is of paramount importance. In this article, we have compiled 104 adult mastocytosis cases diagnosed and followed in our Hematology and other clinics. 86 (82.7%) of 104 patients had systemic mastocytosis. Osteoporosis, disease-related complications, and secondary malignancies are important topics in this group. We know that indolent form has great survival. But smoldering or aggressive mastocytosis has a poor prognosis. CM and indolent SM have a significantly better prognosis compared to aggressive SM (p < 0.001). We found that the presence of more than 25% of mast cells in the bone marrow, the presence of concomitant marrow dysplasia, and the presence of disease-related complications affect survival (p < 0.001). In addition to the WHO classification, the IPSM scoring system is indicative of the prognosis in this rare disease.

The international consensus classification of mastocytosis and related entities

Mastocytosis is a neoplasm characterized by a clonal proliferation of mast cells, which accumulate in one or multiple organs, associated with an extremely heterogeneous clinical presentation. The disease can be limited to the skin (cutaneous mastocytosis) that is mostly seen in childhood and usually behaves in a benign fashion. Adult patients most often present with systemic disease with or without skin lesions. This includes indolent forms such as indolent systemic mastocytosis and its subvariant bone marrow mastocytosis, and smoldering systemic mastocytosis as well as aggressive forms including aggressive systemic mastocytosis, systemic mastocytosis with an associated myeloid neoplasm (previously called systemic mastocytosis with an associated hematologic neoplasm), and mast cell leukemia. In addition, mast cell sarcoma is a rare aggressive form of mastocytosis that can present in the skin as well as at extracutaneous sites. This review article focuses on the updates in mastocytosis of the 2022 international consensus classification (ICC).

Immunohistochemical Staining to Identify Concomitant Systemic Mastocytosis in Acute Myeloid Leukemia with RUNX1::RUNX1T1

Systemic mastocytosis with associated hematological neoplasm (SM-AHN) poses diagnostic challenges because of the coexistence of atypical mast cell proliferation and hematological neoplasms. We assessed the presence of SM-AHN in patients with acute myeloid leukemia (AML) with RUNX1::RUNX1T1 from 2014 to 2020. Bone marrow (BM) samples were evaluated for mast cell aggregates using CD117 and CD25 immunohistochemical (IHC) staining. The KIT D816V variant burden at diagnosis and post induction was assessed using droplet digital PCR. Among 23 patients diagnosed as having AML with RUNX1::RUNX1T1, four (17.4%) were also diagnosed as having SM-AHN. No significant differences in clinical characteristics or overall survival (P=0.565) were observed between patients with or without SM-AHN, except for the presence of KIT variants (P=0.040). After induction therapy, IHC staining revealed the presence of mast cell aggregates in the BM, and the KIT D816V variant burden decreased with decreasing blast count and was similar in BM aspirates, smear slides, and sections. Concomitant SM-AHN was not infrequent in AML patients with RUNX1::RUNX1T1. This study showed the importance of CD117 and CD25 IHC staining after induction chemotherapy for SM-AHN screening, especially in patients with KIT variants.

Proposed European Competence Network on Mastocytosis-American Initiative in Mast Cell Diseases (ECNM-AIM) Response Criteria in Advanced Systemic Mastocytosis

Advanced systemic mastocytosis (AdvSM) is characterized by the presence of KIT D816V and other somatic mutations (eg, in SRSF2, ASXL1, and RUNX1) in 95% and 60% to 70% of patients, respectively. The biological and clinical consequences of AdvSM include multilineage involvement (eg, associated hematologic neoplasm) in 60% to 80% of patients, variable infiltration and damage (C-findings) of predominantly bone marrow and visceral organs through affected mast cell (MC) and non-MC lineages, and elevated levels of serum tryptase. Recently, the treatment landscape has substantially changed with the introduction of the multikinase/KIT inhibitor midostaurin and the selective KIT D816V inhibitor avapritinib. In this review, we discuss the evolution of AdvSM response criteria that have been developed to better capture clinical benefit (eg, improved responses and progression-free and overall survival). We propose refined response criteria from European Competence Network on Mastocytosis and American Initiative in Mast Cell Diseases investigators that use a tiered approach to segregate the effects of histopathologic (eg, bone marrow MC burden, tryptase), molecular (eg, KIT D816V variant allele frequency), clinical (eg, C-findings), and symptom response on long-term outcomes. These response criteria require evaluation in future prospective clinical trials of selective KIT inhibitors and other novel agents.

Systemic Mastocytosis and Other Entities Involving Mast Cells: A Practical Review and Update

Evidence in the recent literature suggests that the presentation spectrum of mast cell neoplasms is broad. In this article, we elaborate on recent data pertaining to minor diagnostic criteria of systemic mastocytosis (SM), including sensitive testing methods for detection of activating mutations in the KIT gene or its variants, and adjusted serum tryptase levels in cases with hereditary α-tryptasemia. We also summarize entities that require differential diagnosis, such as the recently reclassified SM subtype named bone marrow mastocytosis, mast cell leukemia (an SM subtype that can be acute or chronic); the rare morphological variant of all SM subtypes known as well-differentiated systemic mastocytosis; the extremely rare myelomastocytic leukemia and its differentiating features from mast cell leukemia; and mast cell activation syndrome. In addition, we provide a concise clinical update of the latest adjusted risk stratification model incorporating genomic data to define prognosis in SM and new treatments that were approved for advanced SM (midostaurin, avapritinib).

Systemic Mastocytosis: Advances in Diagnosis and Current Management

Mastocytosis is a rare hematologic disorder characterized by abnormal proliferation and accumulation of neoplastic mast cells in various body sites. Isolated skin involvement is termed cutaneous mastocytosis (CM) and the term systemic mastocytosis (SM) refers to multi-organ involvement, most commonly of the bone marrow, skin, liver, and spleen. A subset of patients with SM have an associated clonal hematologic neoplasm which is most commonly myelodysplastic syndrome, chronic myelomonocytic leukemia, or acute myelogenous leukemia and this entity is termed SM with associated hematological neoplasm (AHN). Bone marrow involvement is present in all patients regardless of the subtype of SM. The genetic hallmark of SM is a somatic gain-of-function point mutation within the KIT gene. Other molecular aberrations that have been reported include somatic mutations in TET2, SRSF2, ASXL1, CBL, RUNX1, and RAS and these are common in SM-AHN. The clinical presentation of SM can range from indolent to advanced depending on extent of mast cell burden and genetic profile. In the case of indolent SM, the goal of treatment is to control mediator release-related effects as well as to reduce mast cell burden. In the case of SM-AHN, therapy is primarily that of the AHN and allogeneic hematopoietic stem cell transplantation is the preferred therapy in suitable candidates.

Mastocytosis

OBJECTIVES

The 2019 Workshop of the Society for Hematopathology/European Association for Haematopathology received and reviewed cases covering the spectrum of mastocytosis and related diseases, including morphologic mimics, focusing on recent updates and relevant findings for pathologists.

METHODS

The workshop panel reviewed 99 cases of cutaneous and systemic mastocytosis (SM) and SM and associated hematologic neoplasms (SM-AHN).

RESULTS

Despite a common theme of KIT mutation (particularly D816V), mastocytosis is a heterogeneous neoplasm with a wide variety of presentations. This spectrum, including rare subtypes and extramedullary organ involvement, is discussed and illustrated by representative cases.

CONCLUSIONS

In the age of targeted treatment aimed at KIT, the accurate diagnosis and classification of mastocytosis has major implications for therapy and further interventions. Understanding the clinical, pathologic, and genetic findings of mastocytosis is crucial for selecting the proper tests to perform and subsequent arrival at a correct diagnosis in this rare disease.

Detection of the KITD816V mutation in myelodysplastic and/or myeloproliferative neoplasms and acute myeloid leukemia with myelodysplasia-related changes predicts concurrent systemic mastocytosis

Greater than 90% of cases of systemic mastocytosis (SM) harbor pathogenic KIT mutations, particularly KIT^D816V. Prognostically-significant pathogenic KIT mutations also occur in 30-40% of core binding factor-associated acute myeloid leukemia (CBF-AML), but are uncommonly associated with concurrent SM. By comparison, the occurrence of SM in other myeloid neoplasms bearing pathogenic KIT mutations, particularly those with a chronic course, is poorly understood. Review of clinical next-generation sequencing (NGS) performed at our institutions in patients with known or suspected hematologic malignancies over an 8-year period revealed 64 patients with both a pathogenic KIT mutation detected at one or more timepoints and available bone marrow biopsy materials. Patients with KIT^D816V-mutated myelodysplastic syndromes (MDS), myeloproliferative neoplasms (MPN), or overlap MDS/MPN (n = 22) accounted for approximately one-third of our cohort (34%). Comprehensive morphologic and immunophenotypic characterization revealed that nearly all cases (n = 20, 91%) exhibited concurrent SM. In contrast, of the 18 patients (28%) with AML and KIT^D816V, only eight (44%) showed evidence of SM at any point in their disease course (p = 0.0021); of these eight, the AML component was characterized as AML with myelodysplasia-related changes (AML-MRC) in all but one instance (n = 7, 87%). Twelve patients (19%) had pathogenic KIT mutations other than p.D816V, all in the setting of AML (CFB-AML, n = 7; AML, not otherwise specified, n = 2; AML-MRC, n = 1; acute promyelocytic leukemia, n = 1); only two of these patients (17%), both with CBF-AML, exhibited concurrent SM. The remaining 12 patients (19%) had SM without evidence of an associated hematological neoplasm (AHN). For nearly one-third of the 30 SM-AHN patients in our cohort (n = 9, 30%), the SM component of their disease was not initially clinicopathologically recognized. We propose that identification of the KIT^D816V mutation in patients diagnosed with MDS, MPN, MDS/MPN, or AML-MRC should trigger reflex testing for SM.

A Rare Case of Systemic Mastocytosis with Associated Hematologic Neoplasm (SM-AHN) Involving Chronic Myeloid Leukemia: A Case Report and Literature Review

BACKGROUND Single or multiple cell line dysplasia is a characteristic feature of myelodysplastic syndrome. However, significant dysgranulopoiesis is not a feature of chronic myeloid leukemia (CML). Systemic mastocytosis (SM) with an associated hematologic neoplasm (SM-AHN) comprises 5% to 40% of cases of SM. All types of hematologic neoplasms have been previously reported, although CML has been rarely encountered. CASE REPORT A 28-year-old male presented with a 3-month-history of weight loss and massive splenomegaly. Peripheral blood revealed marked leukocytosis, shift to left with 13% blasts. There was evident dysgranulopoiesis that raised a provisional diagnosis of myelodysplastic/myeloproliferative neoplasm. Bone marrow (BM) examination revealed granulocytic hyperplasia with 10% blasts and significant dysgranulopoiesis. Unexpectedly, cytogenetic analysis revealed t(9;22) with BCR/ABL1 rearrangement, diagnostic of chronic myeloid leukemia in an accelerated phase. The patient was started on dasatinib 100 mg upfront, however, he failed to respond, with increasing leukocytosis. Repeat BM examination showed persistence of the findings with 8% blasts. At this time, aggregates of mast cells with aberrant expression of CD25 were elicited, thus concluding the diagnosis of SM-AHN. The patient failed multiple lines of treatment (dasatinib, nilotinib, hydroxyurea, cytarabine subcutaneous, 6-mercaptopurine and interferon) and progressed to the blast phase a few months later. CONCLUSIONS We report an unusual case of CML, presented with significant dysgranulopoiesis with an aggressive clinical course including SM uncovered during the disease course with subsequent transformation to the blast phase. The different biological behavior of this case underscores the need for studies on a larger number of cases to explore the significance of the aforementioned coexistent features.

New developments in diagnosis, prognostication, and treatment of advanced systemic mastocytosis

Systemic mastocytosis (SM) has greatly benefited from the broad application of precision medicine techniques to hematolymphoid neoplasms. Sensitive detection of the recurrent KIT D816V mutation and use of next-generation sequencing (NGS) panels to profile the genetic landscape of SM variants have been critical adjuncts to the diagnosis and subclassification of SM, and development of clinical-molecular prognostic scoring systems. Multilineage KIT involvement and multimutated clones are characteristic of advanced SM (advSM), especially SM with an associated hematologic neoplasm (AHN). A major challenge is how to integrate conventional markers of mast cell disease burden (percentage of bone marrow mast cell infiltration and serum tryptase levels) with molecular data (serial monitoring of both KIT D816V variant allele frequency and NGS panels) to lend more diagnostic and prognostic clarity to the heterogeneous clinical presentations and natural histories of advSM. The approval of the multikinase/KIT inhibitor midostaurin has validated the paradigm of KIT inhibition in advSM, and the efficacy and safety of second-generation agents, such as the switch-control inhibitor ripretinib (DCC-2618) and the D816V-selective inhibitor avapritinib (BLU-285) are being further defined in ongoing clinical trials. Looking forward, perhaps the most fruitful marriage of the advances in molecular genetics and treatment will be the design of adaptive basket trials that combine histopathology and genetic profiling to individualize treatment approaches for patients with diverse AHNs and relapsed/refractory SM.

The Spectrum of Aggressive Mastocytosis: A Workshop Report and Literature Review

Most cases of mastocytosis are indolent, usually cutaneous mastocytosis or indolent systemic mastocytosis (SM). Aggressive mast cell (MC) diseases are very rare and often fatal. They can develop de novo or due to progression of indolent forms and can present in different ways; either as MC sarcoma or as advanced SM which includes aggressive SM, MC leukemia, and SM with an associated hematological neoplasm. This review will describe these different aggressive forms of mastocytosis, illustrated by cases submitted to the workshop of the 18th Meeting of the European Association for Haematopathology, Basel 2016, organized by the European Bone Marrow Working Group. In addition, the diagnostic criteria for identifying myelomastocytic leukemia, an aggressive myeloid neoplasm with partial MC differentiation that falls short of the criteria for SM, and disease progression in patients with established mastocytosis are discussed.

Acute myeloid leukemia with t(8;21)(q22;q22.1)/RUNX1-RUNX1T1 and KIT Exon 8 mutation is associated with characteristic mastocytosis and dismal outcomes

KIT mutations are observed in about 20-40% of acute myeloid leukemia with t(8;21)(q22;q22.1)/RUNX1-RUNX1T1 [abbreviated AML t(8;21) here] with mutations involving exon 17 being the most common. Despite high frequencies of KIT mutations in both AML t(8;21) and systemic mastocytosis (SM), AML t(8;21) associated with SM is uncommon, and restricted to KIT exon 17 mutated cases. In this study, we report two cases of AML t(8;21) associated SM that KIT mutation occurred in exon 8 (T417_D419delinsY). In both patients, the bone marrow displayed increased round/ovoid mast cells with bilobated nuclei and absence of CD2 and CD25 expression. RUNX1/RUNX1T1 fusion was shown in both myeloblasts and mast cells by FISH. Patient #1 was refractory to induction chemotherapy and died at day 50; patient #2 had residual AML, marked SM, and persistent RUNX1/RUNX1T1 fusion after induction therapy.

Identification of chromosomal abnormalities and genomic features in near-triploidy/tetraploidy-acute leukemia by fluorescence in situ hybridization

Background

Near-triploidy/tetraploidy is rarely found in acute leukemia. Only limited data are available to characterize this condition, and it remains largely unknown.

Patients and methods

In our study, we performed karyotype analysis on 1,031 patients diagnosed with acute leukemia from 2006 to 2018. A total of 10 patients of near-triploidy/tetraploidy karyotype were enrolled. Two cases of near-triploidy (66-79 chromosomes) and eight cases of near-tetraploidy (84-100 chromosomes) were identified. Bone marrow samples of these 10 patients were analyzed by fluorescence in situ hybridization with 19 commercially available probes that detected a small portion of gene alterations and large regions of chromosome amplifications.

Results

Of the six patients with acute myelocytic leukemia, we detected three cases of double t(8;21)(q22;q22) that have not been previously reported, and one of them demonstrated ins(21;8) (q22;q24q22). We also describe a novel pediatric case carrying double t(15;17)(q22;q21) and receiving targeted treatment with all-trans retinoic acid therapy. To date, this case has responded well to the regimen and has shown continuous complete remission. All patients received chemotherapy. One of them received allogeneic hematopoietic stem cell transplant (HSCT) and survived for 22 months. Eight of the 10 patients died, and the median overall survival was 11 months.

Conclusion

Using fluorescence in situ hybridization, we identified the distinct complex karyotype of near-triploidy/tetraploidy and provided further prognostic information. Tetraploidy acute promyelocytic leukemia had favorable prognosis; thus, HSCT was not necessary. The case of insertion t(21;8)(q22;q24q22) in tetraploidy responded poorly to chemotherapy and achieved molecular remission with difficultly. Data from patients in this group indicated that near-triploidy/tetraploidy acute leukemia has poor prognosis and new therapy is urgently needed.

Acute Myeloid Leukemia With Inv(16)(p13q22) Associated With Hidden Systemic Mastocytosis: Case Report and Review of Literature

Systemic mastocytosis (SM) is a condition associated with clonal neoplastic proliferation of mast cells. In up to 40% of systemic mastocytosis cases, an associated clonal hematological disease of non-mast cell lineage, such as acute myeloid leukemia (AML), is diagnosed before, simultaneously with, or after the diagnosis of SM. Herein, we report a case of a 30-year-old man diagnosed with AML with inv(16) (p13;q22) CBFB:MYH11. Associated mastocytosis was not noted at diagnosis and was only detected in the bone marrow at time of remission after successful chemotherapy. The diagnosis of mastocytosis was based on the demonstration of a multifocal dense mast cell infiltrate in the marrow biopsy with aberrant immunophenotype, with coexpression of tryptase, CD117, and CD25. The mast cells showed atypical morphology mostly with irregular nuclear contour, bilobed or multilobed nuclei with cytoplasmic hypogranulation or irregular metachromatic granule distribution, and some cells with eccentric nucleus or spindle shape. Reexamination of the pretherapeutic bone marrow with immunostain for tryptase and CD25 revealed that mastocytosis was present from the start but masked by extensive blast proliferation. This case indicates that mast cell infiltrates are sometimes underappreciated at the original diagnosis of AML with inv(16) and that the concurrent diagnosis of SM with AML requires a high index of suspicion supported with comprehensive morphologic and immunohistochemical evaluation for a neoplastic mast cell proliferation.

Shared clonal cytogenetic abnormalities in aberrant mast cells and leukemic myeloid blasts detected by single nucleotide polymorphism microarray-based whole-genome scanning

Systemic mastocytosis (SM) is characterized by a clonal proliferation of aberrant mast cells within extracutaneous sites. In a subset of SM cases, a second associated hematologic non-mast cell disease (AHNMD) is also present, usually of myeloid origin. Polymerase chain reaction and targeted fluorescence in situ hybridization studies have provided evidence that, in at least some cases, the aberrant mast cells are related clonally to the neoplastic cells of the AHNMD. In this work, a single nucleotide polymorphism microarray (SNP-A) was used to characterize the cytogenetics of the aberrant mast cells from a patient with acute myeloid leukemia and concomitant mast cell leukemia associated with a KIT D816A mutation. The results demonstrate the presence of shared cytogenetic abnormalities between the mast cells and myeloid blasts, as well as additional abnormalities within mast cells (copy-neutral loss of heterozygosity) not detectable by routine karyotypic analysis. To our knowledge, this work represents the first application of SNP-A whole-genome scanning to the detection of shared cytogenetic abnormalities between the two components of a case of SM-AHNMD. The findings provide additional evidence of a frequent clonal link between aberrant mast cells and cells of myeloid AHNMDs, and also highlight the importance of direct sequencing for identifying uncommon activating KIT mutations.

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.

Mast cells in systemic mastocytosis have distinctly brighter CD45 expression by flow cytometry

OBJECTIVES

We sought to determine the significance of bright CD45 expression on mast cells in cases of systemic mastocytosis vs mast cells in bone marrows uninvolved by systemic mastocytosis and compare this CD45 expression with CD25 and CD2 expression on mast cells.

METHODS

Multiparameter flow cytometry was performed on 31 cases of systemic mastocytosis and 70 bone marrow cases that were not involved by systemic mastocytosis. Bright expression of CD45 was defined as more than 20% of CD117+ mast cells showing brighter CD45 expression than the average expression level of lymphocytes.

RESULTS

Mast cells with bright CD45 expression were seen in 26 systemic mastocytosis cases and three bone marrows uninvolved by systemic mastocytosis (sensitivity, 84%; specificity, 96%). CD25 alone had a greater sensitivity (100%) but lower specificity (93%) compared with bright CD45 for identifying abnormal mast cells, while CD2 alone had lower sensitivity but higher specificity. To reach a specificity of 100%, CD25 together with bright CD45 on mast cells was the optimal combination to detect cases of systemic mastocytosis.

CONCLUSIONS

A combination of bright CD45 and CD25 appears to specifically identify abnormal mast cells in cases of systemic mastocytosis. Further studies will be necessary to confirm these results.

Mast cell leukemia: a review

SUMMARY 

Mast cell leukemia (MCL) is a rare subtype of systemic mastocytosis. In MCL the numbers of mast cells exceed 19% of nucleated cells in bone marrow and/or 10% of circulating leukocytes in peripheral blood. Primary MCL must be distinguished from secondary MCL evolving from another subvariant of systemic mastocytosis or from mast cell sarcoma. Acute MCL with a poor prognosis is distinguished from the more indolent chronic MCL. Serum tryptase is significantly elevated in almost all MCL patients and activating point mutations at codon 816 of KIT (usually KIT D816V) are encountered in about 70%. Regarding differential diagnosis, other ‘tryptase-positive’ or ‘metachromatic’ leukemias must be considered, including myelomastocytic leukemia and tryptase-positive acute myeloid leukemia but also acute and chronic basophilic leukemias.

Core-binding factor acute myeloid leukemia: Heterogeneity, monitoring, and therapy

Core binding factor acute myelogenous leukemia (CBF AML) constitutes 15% of adult AML and carries an overall good prognosis. CBF AML encodes two recurrent cytogentic abnormalities referred to as t(8;21) and inv (16). The two CBF AML entities are usually grouped together but there is a considerable clinical, pathologic and molecular heterogeneity within this group of diseases. Recent and ongoing studies are addressing the molecular heterogeneity, minimal residual disease and targeted therapies to improve the outcome of CBF AML. In this article, we present a comprehensive review about CBF AML with emphasis on molecular heterogeneity and new therapeutic options.

The serum tryptase test: an emerging robust biomarker in clinical hematology

During the past few years, a number of molecular markers have been developed in clinical hematology, most of them related to specific gene defects. However, there is also an unmet need to develop novel serologic parameters to improve diagnostics and prognostication in daily practice. Among these, the serum tryptase appears to be a most reliable biomarker of myeloid neoplasms. Elevated tryptase levels are found in subgroups of patients with mastocytosis, myelodysplastic syndrome, myeloproliferative neoplasm, acute myeloid leukemia, chronic myeloid leukemia and chronic eosinophilic leukemia. In these patients, the tryptase level is of diagnostic and/or prognostic significance. In mastocytosis, an elevated tryptase level is a minor criterion of systemic disease and in BCR-ABL1(+) chronic myeloid leukemia, elevated tryptase at diagnosis correlates with treatment responses and overall survival. In patients with elevated tryptase, the enzyme also serves as follow-up parameter and can be employed to measure treatment-responses. In the current article, we review and update the perspectives of tryptase and provide recommendations for use of this conventional biomarker in daily practice.

Hematopoietic stem-cell transplantation for advanced systemic mastocytosis

PURPOSE

Advanced systemic mastocytosis (SM), a fatal hematopoietic malignancy characterized by drug resistance, has no standard therapy. The effectiveness of allogeneic hematopoietic stem-cell transplantation (alloHCT) in SM remains unknown.

PATIENTS AND METHODS

In a global effort to define the value of HCT in SM, 57 patients with the following subtypes of SM were evaluated: SM associated with clonal hematologic non-mast cell disorders (SM-AHNMD; n = 38), mast cell leukemia (MCL; n = 12), and aggressive SM (ASM; n = 7). Median age of patients was 46 years (range, 11 to 67 years). Donors were HLA-identical (n = 34), unrelated (n = 17), umbilical cord blood (n = 2), HLA-haploidentical (n = 1), or unknown (n = 3). Thirty-six patients received myeloablative conditioning (MAC), and 21 patients received reduced-intensity conditioning (RIC).

RESULTS

Responses in SM were observed in 40 patients (70%), with complete remission in 16 patients (28%). Twelve patients (21%) had stable disease, and five patients (9%) had primary refractory disease. Overall survival (OS) at 3 years was 57% for all patients, 74% for patients with SM-AHNMD, 43% for those with ASM, and 17% for those with MCL. The strongest risk factor for poor OS was MCL. Survival was also lower in patients receiving RIC compared with MAC and in patients having progression compared with patients having stable disease or response.

CONCLUSION

AlloHCT was associated with long-term survival in patients with advanced SM. Although alloHCT may be considered as a viable and potentially curative therapeutic option for advanced SM in the meantime, given that this is a retrospective analysis with no control group, the definitive role of alloHCT will need to be determined by a prospective trial.