Real world predictors of response and 24-month survival in high-grade TP53-mutated myeloid neoplasms.

Current therapies for high-grade TP53-mutated myeloid neoplasms (≥10% blasts) do not offer a meaningful survival benefit except allogeneic stem cell transplantation in the minority who achieve a complete response to first line therapy (CR1). To identify reliable pre-therapy predictors of complete response to first-line therapy (CR1) and outcomes, we assembled a cohort of 242 individuals with TP53-mutated myeloid neoplasms and ≥10% blasts with well-annotated clinical, molecular and pathology data. Key outcomes examined were CR1 & 24-month survival (OS24). In this elderly cohort (median age 68.2 years) with 74.0% receiving frontline non-intensive regimens (hypomethylating agents +/- venetoclax), the overall cohort CR1 rate was 25.6% (50/195). We additionally identified several pre-therapy factors predictive of inferior CR1 including male gender (P = 0.026), ≥2 autosomal monosomies (P < 0.001), -17/17p (P = 0.011), multi-hit TP53 allelic state (P < 0.001) and CUX1 co-alterations (P = 0.010). In univariable analysis of the entire cohort, inferior OS24 was predicated by ≥2 monosomies (P = 0.004), TP53 VAF > 25% (P = 0.002), TP53 splice junction mutations (P = 0.007) and antecedent treated myeloid neoplasm (P = 0.001). In addition, mutations/deletions in CUX1, U2AF1, EZH2, TET2, CBL, or KRAS ('EPI6' signature) predicted inferior OS24 (HR = 2.0 [1.5-2.8]; P < 0.0001). In a subgroup analysis of HMA +/-Ven treated individuals (N = 144), TP53 VAF and monosomies did not impact OS24. A risk score for HMA +/-Ven treated individuals incorporating three pre-therapy predictors including TP53 splice junction mutations, EPI6 and antecedent treated myeloid neoplasm stratified 3 prognostic distinct groups: intermediate, intermediate-poor, and poor with significantly different median (12.8, 6.0, 4.3 months) and 24-month (20.9%, 5.7%, 0.5%) survival (P < 0.0001). For the first time, in a seemingly monolithic high-risk cohort, our data identifies several baseline factors that predict response and 24-month survival.

Socioeconomic determinants of the biology and outcomes of acute lymphoblastic leukemia in adults.

ABSTRACT: Various socioeconomic and biologic factors affect cancer health disparities and differences in health outcomes. To better characterize the socioeconomic vs biologic determinants of acute lymphoblastic leukemia (ALL) outcomes, we conducted a single-institution, retrospective analysis of adult patients with ALL treated at the University of Chicago (UChicago) from 2010 to 2022 and compared our outcomes with the US national data (the Surveillance, Epidemiology, and End Results [SEER] database). Among 221 adult patients with ALL treated at UChicago, BCR::ABL1 was more frequent in patients with higher body mass index (BMI; odds ratio [OR], 7.64; 95% confidence interval [CI], 1.17-49.9) and non-Hispanic Black (NHB) ancestry (59% vs 24% in non-Hispanic White (NHW) and 20% in Hispanic patients; P = .001). In a multivariable analysis, age (hazard ratio [HR], 6.93; 95% CI, 2.27-21.1) and higher BMI at diagnosis (HR, 10.3; 95% CI, 2.56-41.5) were independent predictors of poor overall survival (OS). In contrast, race or income were not predictors of OS in the UChicago cohort. Analysis of the national SEER database (2010-2020) demonstrated worse survival outcomes in Hispanic and NHB patients than in NHW patients among adolescent and young adults (AYAs) but not in older adults (aged >40 years). Both AYA and older adult patients with higher median household income had better OS than those with lower income. Therefore, multidisciplinary medical care coupled with essential supportive care services offered at centers experienced in ALL care may alleviate the socioeconomic disparities in ALL outcomes in the United States.

Acute Lymphoblastic Leukemia with Myeloid Mutations Is a High-Risk Disease Associated with Clonal Hematopoiesis.

Myeloid neoplasms arise from preexisting clonal hematopoiesis (CH); however, the role of CH in the pathogenesis of acute lymphoblastic leukemia (ALL) is unknown. We found that 18% of adult ALL cases harbored TP53, and 16% had myeloid CH-associated gene mutations. ALL with myeloid mutations (MyM) had distinct genetic and clinical characteristics, associated with inferior survival. By using single-cell proteogenomic analysis, we demonstrated that myeloid mutations were present years before the diagnosis of ALL, and a subset of these clones expanded over time to manifest as dominant clones in ALL. Single-cell RNA sequencing revealed upregulation of genes associated with cell survival and resistance to apoptosis in B-ALL with MyM, which responds better to newer immunotherapeutic approaches. These findings define ALL with MyM as a high-risk disease that can arise from antecedent CH and offer new mechanistic insights to develop better therapeutic and preventative strategies. SIGNIFICANCE: CH is a precursor lesion for lymphoblastic leukemogenesis. ALL with MyM has distinct genetic and clinical characteristics, associated with adverse survival outcomes after chemotherapy. CH can precede ALL years before diagnosis, and ALL with MyM is enriched with activated T cells that respond to immunotherapies such as blinatumomab. See related commentary by Iacobucci, p. 142.

Ozanimod-Exposed Patients with Ulcerative Colitis Undergoing Total Colectomy Exhibit Unique Lymph Node Histologic Changes.

INTRODUCTION: Ozanimod regulates lymphocyte egress from the spleen and lymph nodes into the systemic circulation. The histologic changes which occur in the lymph nodes of patients on ozanimod is unknown. MATERIALS AND METHODS: This retrospective study included patients with UC undergoing total colectomy for treatment-refractory disease who received ozanimod and a cohort of patients with UC undergoing colectomy who did not have ozanimod exposure. Histology of the lymph nodes from the mesentery of colectomy specimens was reviewed and multiple features were scored by experienced pathologists. RESULTS: Six (13%) ozanimod-treated patients with UC required surgery for treatment-refractory disease. Colectomy specimen data were available for 5 patients (1 patient had surgery at an outside center). Lymph node specimens from 6 control patients with UC who had colectomy were examined. Histologic examination of lymph nodes showed that patients treated with ozanimod had significantly greater extent of dilated sinuses (p=0.03) and greater degrees of sinus histiocytosis (p=0.03) compared with control patients. In addition, there was a trend towards more Castleman-like angiotrophic hyperplasia, plasma cell infiltration and subcortical interfollicular expansion in ozanimod treated patients. CONCLUSION: This study identifies unique histologic changes in the lymph nodes of patients with UC treated with ozanimod. The presence of sinus histiocytosis and dilated sinuses is in keeping with the known mechanism of action of ozanimod and suggests that blocking lymphocyte egression from lymph nodes was insufficient to ameliorate disease severity in these patients. The possibility of Castleman-like features identified in several of the cases, needs to be further investigated.

GLUT1 Immunohistochemistry Is a Highly Sensitive and Relatively Specific Marker for Erythroid Lineage in Benign and Malignant Hematopoietic Tissues.

OBJECTIVES: Glucose transporter 1 (GLUT1), a glucose transporter, is an abundant protein in erythrocytes with expression beginning early in erythropoiesis. We sought to evaluate the utility of GLUT1 immunohistochemistry (IHC) as a diagnostic marker for identifying erythroid differentiation in hematopoietic tissues, including neoplastic erythroid proliferations. METHODS: A variety of benign and neoplastic bone marrow biopsy specimens containing variable proportions of erythroid precursors were selected (n = 46, including 36 cases of leukemia). GLUT1 IHC was performed using a commercially available polyclonal antibody. Each case was evaluated for staining of erythroid precursors, nonerythroid hematopoietic cells, and blasts. A GATA1/GLUT1 double stain was performed on one case to confirm coexpression of GLUT1 on early erythroid precursors. Staining was compared with other erythroid markers, including glycophorin C. RESULTS: GLUT1 demonstrated strong membranous staining in erythroid precursors of all cases, which was restricted largely to the erythroid lineage. Of the 36 leukemia cases, all 6 cases of pure erythroid leukemia and both cases of therapy-related acute myeloid leukemia with erythroid differentiation showed positive GLUT1 staining in blasts. Otherwise, only lymphoblasts in B-lymphoblastic leukemia showed weak to moderate granular cytoplasmic staining (four of five cases). CONCLUSIONS: GLUT1 IHC is a highly sensitive and relatively specific marker for erythroid lineage in benign and neoplastic bone marrow biopsy specimens.

RNA Epigenetics: Fine-Tuning Chromatin Plasticity and Transcriptional Regulation, and the Implications in Human Diseases.

Chromatin structure plays an essential role in eukaryotic gene expression and cell identity. Traditionally, DNA and histone modifications have been the focus of chromatin regulation; however, recent molecular and imaging studies have revealed an intimate connection between RNA epigenetics and chromatin structure. Accumulating evidence suggests that RNA serves as the interplay between chromatin and the transcription and splicing machineries within the cell. Additionally, epigenetic modifications of nascent RNAs fine-tune these interactions to regulate gene expression at the co- and post-transcriptional levels in normal cell development and human diseases. This review will provide an overview of recent advances in the emerging field of RNA epigenetics, specifically the role of RNA modifications and RNA modifying proteins in chromatin remodeling, transcription activation and RNA processing, as well as translational implications in human diseases.

OTS167 blocks FLT3 translation and synergizes with FLT3 inhibitors in FLT3 mutant acute myeloid leukemia.

Internal tandem duplication (-ITD) mutations of Fms-like tyrosine kinase 3 (FLT3) provide growth and pro-survival signals in the context of established driver mutations in FLT3 mutant acute myeloid leukemia (AML). Maternal embryonic leucine zipper kinase (MELK) is an aberrantly expressed gene identified as a target in AML. The MELK inhibitor OTS167 induces cell death in AML including cells with FLT3 mutations, yet the role of MELK and mechanisms of OTS167 function are not understood. OTS167 alone or in combination with tyrosine kinase inhibitors (TKIs) were used to investigate the effect of OTS167 on FLT3 signaling and expression in human FLT3 mutant AML cell lines and primary cells. We describe a mechanism whereby OTS167 blocks FLT3 expression by blocking FLT3 translation and inhibiting phosphorylation of eukaryotic initiation factor 4E-binding protein 1 (4E-BP1) and eukaryotic translation initiation factor 4B (eIF4B). OTS167 in combination with TKIs results in synergistic induction of FLT3 mutant cell death in FLT3 mutant cell lines and prolonged survival in a FLT3 mutant AML xenograft mouse model. Our findings suggest signaling through MELK is necessary for the translation and expression of FLT3-ITD, and blocking MELK with OTS167 represents a viable therapeutic strategy for patients with FLT3 mutant AML.

The Role of RNA Modifications and RNA-modifying Proteins in Cancer Therapy and Drug Resistance.

The advent of new genome-wide sequencing technologies has uncovered abnormal RNA modifications and RNA editing in a variety of human cancers. The discovery of reversible RNA N6-methyladenosine (RNA: m6A) by fat mass and obesity-associated protein (FTO) demethylase has led to exponential publications on the pathophysiological functions of m6A and its corresponding RNA modifying proteins (RMPs) in the past decade. Some excellent reviews have summarized the recent progress in this field. Compared to the extent of research into RNA: m6A and DNA 5-methylcytosine (DNA: m5C), much less is known about other RNA modifications and their associated RMPs, such as the role of RNA: m5C and its RNA cytosine methyltransferases (RCMTs) in cancer therapy and drug resistance. In this review, we will summarize the recent progress surrounding the function, intramolecular distribution and subcellular localization of several major RNA modifications, including 5' cap N7-methylguanosine (m7G) and 2'-O-methylation (Nm), m6A, m5C, A-to-I editing, and the associated RMPs. We will then discuss dysregulation of those RNA modifications and RMPs in cancer and their role in cancer therapy and drug resistance.

Cytotoxic Therapy-Induced Effects on Both Hematopoietic and Marrow Stromal Cells Promotes Therapy-Related Myeloid Neoplasms.

Therapy-related myeloid neoplasms (t-MNs) following treatment with alkylating agents are characterized by a del(5q), complex karyotypes, alterations of TP53, and a dismal prognosis. To decipher the molecular pathway(s) leading to the pathogenesis of del(5q) t-MN and the effect(s) of cytotoxic therapy on the marrow microenvironment, we developed a mouse model with loss of two key del(5q) genes, EGR1 and APC, in hematopoietic cells. We used the well-characterized drug, N-ethyl-N-nitrosurea (ENU) to demonstrate that alkylating agent exposure of stromal cells in the microenvironment increases the incidence of myeloid disease. In addition, loss of Trp53 with Egr1 and Apc was required to drive the development of a transplantable leukemia, and accompanied by the acquisition of somatic mutations in DNA damage response genes. ENU treatment of mesenchymal stromal cells induced cellular senescence, and led to the acquisition of a senescence-associated secretory phenotype, which may be a critical microenvironmental alteration in the pathogenesis of myeloid neoplasms.

Brucella Periplasmic Protein EipB Is a Molecular Determinant of Cell Envelope Integrity and Virulence.

The Gram-negative cell envelope is a remarkable structure with core components that include an inner membrane, an outer membrane, and a peptidoglycan layer in the periplasmic space between. Multiple molecular systems function to maintain integrity of this essential barrier between the interior of the cell and its surrounding environment. We show that a conserved DUF1849 family protein, EipB, is secreted to the periplasmic space of Brucella species, a monophyletic group of intracellular pathogens. In the periplasm, EipB folds into an unusual 14-stranded ß-spiral structure that resembles the LolA and LolB lipoprotein delivery system, though the overall fold of EipB is distinct from LolA/LolB. Deletion of eipB results in defects in Brucella cell envelope integrity in vitro and in maintenance of spleen colonization in a mouse model of Brucella abortus infection. Transposon disruption of ttpA, which encodes a periplasmic protein containing tetratricopeptide repeats, is synthetically lethal with eipB deletion. ttpA is a reported virulence determinant in Brucella, and our studies of ttpA deletion and overexpression strains provide evidence that this gene also contributes to cell envelope function. We conclude that eipB and ttpA function in the Brucella periplasmic space to maintain cell envelope integrity, which facilitates survival in a mammalian host.IMPORTANCEBrucella species cause brucellosis, a global zoonosis. A gene encoding a conserved DUF1849-family protein, which we have named EipB, is present in all sequenced Brucella and several other genera in the class Alphaproteobacteria The manuscript provides the first functional and structural characterization of a DUF1849 protein. We show that EipB is secreted to the periplasm where it forms a spiral-shaped antiparallel ß protein that is a determinant of cell envelope integrity in vitro and virulence in an animal model of disease. eipB genetically interacts with ttpA, which also encodes a periplasmic protein. We propose that EipB and TtpA function as part of a system required for cell envelope homeostasis in select Alphaproteobacteria.

Periplasmic protein EipA determines envelope stress resistance and virulence in Brucella abortus.

Molecular components of the Brucella abortus cell envelope play a major role in its ability to infect, colonize and survive inside mammalian host cells. In this study, we have defined a role for a conserved gene of unknown function in B. abortus envelope stress resistance and infection. Expression of this gene, which we name eipA, is directly activated by the essential cell cycle regulator, CtrA. eipA encodes a soluble periplasmic protein that adopts an unusual eight-stranded ß-barrel fold. Deletion of eipA attenuates replication and survival in macrophage and mouse infection models, and results in sensitivity to treatments that compromise the cell envelope integrity. Transposon disruption of genes required for LPS O-polysaccharide biosynthesis is synthetically lethal with eipA deletion. This genetic connection between O-polysaccharide and eipA is corroborated by our discovery that eipA is essential in Brucella ovis, a naturally rough species that harbors mutations in several genes required for O-polysaccharide production. Conditional depletion of eipA expression in B. ovis results in a cell chaining phenotype, providing evidence that eipA directly or indirectly influences cell division in Brucella. We conclude that EipA is a molecular determinant of Brucella virulence that functions to maintain cell envelope integrity and influences cell division.

Severe hemophagocytic lymphohistiocytosis in a melanoma patient treated with ipilimumab + nivolumab.

BACKGROUND: Treatment of metastatic melanoma patients with immune checkpoint inhibitors is an important standard of care. Side effects are due to immune activation, can affect virtually all organ systems, and are occasionally severe. Although hematologic toxicity has been reported, we present a case of hemophagocytic lymphohistiocytosis (HLH) due to immune checkpoint inhibitor therapy. CASE PRESENTATION: A patient with metastatic melanoma was treated with one course of ipilimumab + nivolumab and presented 3 weeks later with severe anemia and hyperferritinemia. A bone marrow biopsy revealed necrotic tumor cells, infiltrating T cells, and hemophagocytosis. The patient was treated with high-dose steroids; 12 months later, the patient remains off all therapy and in complete remission of both HLH and metastatic melanoma. CONCLUSIONS: The hemophagocytic syndromes are attributable to dysregulated immune activation and share pathophysiologic mechanisms with immune activation from checkpoint inhibitors. Increasing use of regimens that include immune checkpoint inhibition require vigilant monitoring for immune-activating side effects as they can occasionally be life threatening, as in this case of HLH.

Author Correction: RNA cytosine methylation and methyltransferases mediate chromatin organization and 5-azacytidine response and resistance in leukaemia.

In the originally published version of this Article, the GAPDH loading control blot in Fig. 1a was inadvertently replaced with a duplicate of the DNMT2 blot in the same panel during assembly of the figure. This has now been corrected in both the PDF and HTML versions of the Article.

RNA cytosine methylation and methyltransferases mediate chromatin organization and 5-azacytidine response and resistance in leukaemia.

The roles of RNA 5-methylcytosine (RNA:m5C) and RNA:m5C methyltransferases (RCMTs) in lineage-associated chromatin organization and drug response/resistance are unclear. Here we demonstrate that the RCMTs, namely NSUN3 and DNMT2, directly bind hnRNPK, a conserved RNA-binding protein. hnRNPK interacts with the lineage-determining transcription factors (TFs), GATA1 and SPI1/PU.1, and with CDK9/P-TEFb to recruit RNA-polymerase-II at nascent RNA, leading to formation of 5-Azacitidine (5-AZA)-sensitive chromatin structure. In contrast, NSUN1 binds BRD4 and RNA-polymerase-II to form an active chromatin structure that is insensitive to 5-AZA, but hypersensitive to the BRD4 inhibitor JQ1 and to the downregulation of NSUN1 by siRNAs. Both 5-AZA-resistant leukaemia cell lines and clinically 5-AZA-resistant myelodysplastic syndrome and acute myeloid leukaemia specimens have a significant increase in RNA:m5C and NSUN1-/BRD4-associated active chromatin. This study reveals novel RNA:m5C/RCMT-mediated chromatin structures that modulate 5-AZA response/resistance in leukaemia cells, and hence provides a new insight into treatment of leukaemia.

A Herald of Plasma Cell Myeloma: A Report of Malignant Plasma Cells Identified in Parathyroid Adenoma and a Review of Non-parathyroid Malignancies in Parathyroid Glands.

Involvement of the parathyroid glands by non-parathyroid neoplasia is an infrequent event. Rare cases of metastases to the parathyroid gland have been reported in parathyroidectomies and autopsies of patients with known solid or hematopoietic malignancies. Here, we present a case of atypical clonal plasma cells incidentally identified within a parathyroid adenoma resected for hyperparathyroidism and hypercalcemia, which served as the sentinel event for a subsequent diagnosis of plasma cell myeloma. To our knowledge, this is the only reported case of a hematopoietic malignancy involving a parathyroid adenoma and the only reported case of malignant hematopoietic cells initially detected in parathyroidectomy.

Inhibition of WNT signaling in the bone marrow niche prevents the development of MDS in the Apcdel/+ MDS mouse model.

There is accumulating evidence that functional alteration(s) of the bone marrow (BM) microenvironment contribute to the development of some myeloid disorders, such as myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). In addition to a cell-intrinsic role of WNT activation in leukemia stem cells, WNT activation in the BM niche is also thought to contribute to the pathogenesis of MDS and AML. We previously showed that the Apc-haploinsufficient mice (Apcdel/+ ) model MDS induced by an aberrant BM microenvironment. We sought to determine whether Apc, a multifunctional protein and key negative regulator of the canonical ß-catenin (Ctnnb1)/WNT-signaling pathway, mediates this disease through modulating WNT signaling, and whether inhibition of WNT signaling prevents the development of MDS in Apcdel/+ mice. Here, we demonstrate that loss of 1 copy of Ctnnb1 is sufficient to prevent the development of MDS in Apcdel/+ mice and that altered canonical WNT signaling in the microenvironment is responsible for the disease. Furthermore, the US Food and Drug Administration (FDA)-approved drug pyrvinium delays and/or inhibits disease in Apcdel/+ mice, even when it is administered after the presentation of anemia. Other groups have observed increased nuclear CTNNB1 in stromal cells from a high frequency of MDS/AML patients, a finding that together with our results highlights a potential new strategy for treating some myeloid disorders.

Brucella abortus ΔrpoE1 confers protective immunity against wild type challenge in a mouse model of brucellosis.

The Brucella abortus general stress response (GSR) system regulates activity of the alternative sigma factor, σ(E1), which controls transcription of approximately 100 genes and is required for persistence in a BALB/c mouse chronic infection model. We evaluated the host response to infection by a B. abortus strain lacking σ(E1) (ΔrpoE1), and identified pathological and immunological features that distinguish ΔrpoE1-infected mice from wild-type (WT), and that correspond with clearance of ΔrpoE1 from the host. ΔrpoE1 infection was indistinguishable from WT in terms of splenic bacterial burden, inflammation and histopathology up to 6weeks post-infection. However, Brucella-specific serum IgG levels in ΔrpoE1-infected mice were 5 times higher than WT by 4weeks post-infection, and remained significantly higher throughout the course of a 12-week infection. Total IgG and Brucella-specific IgG levels peaked strongly in ΔrpoE1-infected mice at 6weeks, which correlated with reduced splenomegaly and bacterial burden relative to WT-infected mice. Given the difference in immune response to infection with wild-type and ΔrpoE1, we tested whether ΔrpoE1 confers protective immunity to wild-type challenge. Mice immunized with ΔrpoE1 completely resisted WT infection and had significantly higher serum titers of Brucella-specific IgG, IgG2a and IFN-γ after WT challenge relative to age-matched naïve mice. We conclude that immunization of BALB/c mice with the B. abortus GSR pathway mutant, ΔrpoE1, elicits an adaptive immune response that confers significant protective immunity against WT infection.

MDI 301 suppresses myeloid leukemia cell growth in vitro and in vivo without the toxicity associated with all-trans retinoic acid therapy.

MDI 301 is a novel 9-cis retinoic acid derivative in which the terminal carboxylic acid group has been replaced by a picolinate ester. MDI 301, a retinoic acid receptor-α - agonist, suppressed the growth of several human myeloid leukemia cell lines (HL60, NB4, OCI-M2, and K562) in vitro and induced cell-substrate adhesion in conjunction with upregulation of CD11b. Tumor growth in HL60-injected athymic nude mice was reduced. In vitro, MDI 301 was comparable to all-trans retinoic acid (ATRA) whereas in vivo, MDI 301 was slightly more efficacious than ATRA. Most importantly, unlike what was found with ATRA treatment, MDI 301 did not induce a cytokine response in the treated animals and the severe inflammatory changes and systemic toxicity seen with ATRA did not occur. A retinoid with these characteristics might be valuable in the treatment of promyelocytic leukemia, or, perhaps, other forms of myeloid leukemia.

Indolent T-cell lymphoproliferative disease of the gastrointestinal tract.

Primary gastrointestinal (GI) T-cell lymphoma is an infrequent and aggressive disease. However, rare indolent clonal T-cell proliferations in the GI tract have been described. We report 10 cases of GI involvement by an indolent T-cell lymphoproliferative disease, including 6 men and 4 women with a median age of 48 years (range, 15-77 years). Presenting symptoms included abdominal pain, diarrhea, vomiting, food intolerance, and dyspepsia. The lesions involved oral cavity, esophagus, stomach, small intestine, and colon. The infiltrates were dense, but nondestructive, and composed of small, mature-appearing lymphoid cells. Eight cases were CD4(-)/CD8(+), 1 was CD4(+)/CD8(-), and another was CD4(-)/CD8(-). T-cell receptor-γ chain gene rearrangement identified a clonal population in all 10 cases. There was no evidence of STAT3 SH2 domain mutation or activation. Six patients received chemotherapy because of an initial diagnosis of peripheral T-cell lymphoma, with little or no response, whereas the other 4 were followed without therapy. After a median follow-up of 38 months (range, 9-175 months), 9 patients were alive with persistent disease and 1 was free of disease. We propose the name "indolent T-LPD of the GI tract" for these lesions that can easily be mistaken for intestinal peripheral T-cell lymphoma, and lead to aggressive therapy.

Orbital myeloid sarcoma in an adult with acute myeloid leukemia, FAB M1, and 12p-deletion.

A 49-year-old woman with acute myeloid leukemia, FAB M1 subtype, and 12p deletion, presented with progressive right proptosis and diplopia for 1 week. Orbital CT revealed a homogenously enhancing, orbital mass engulfing the inferior rectus muscle. Histopathology revealed myeloid sarcoma for which she underwent external beam radiotherapy. Subsequently, there was no sign of local recurrence, but she succumbed to leukemia involving the central nervous system. This is the first case, to the authors' knowledge, of an orbital sarcoma of FAB M1 myeloblasts bearing a 12p deletion.