Granulocytic sarcoma: 32 cases and review of the literature

Pancreatic Myeloid Sarcoma Causing Obstructive Jaundice: A Case Report and Literature Review

Myeloid sarcoma (MS) is an extramedullary manifestation of acute myeloid leukemia (AML) and commonly occurs in sites such as the lymph nodes, skin, soft tissues, and bone. It more rarely manifests in the pancreas, with less than 20 cases reported in the literature since 1987. Despite its rarity, MS should be considered in the differential diagnosis of a soft tissue mass causing obstructive jaundice, especially if the patient has a known hematologic disease. Isolated cases of pancreatic MS have been known to progress to AML; therefore, it is crucial to differentiate MS from more common diagnoses, such as pancreatic cancer or pancreatitis. This is a case of a 70-year-old male with symptomatic obstructive jaundice secondary to pancreatic MS, ultimately requiring endoscopic ultrasound (EUS) and endoscopic retrograde cholangiopancreatography (ERCP) for diagnosis and management. Also included is a comprehensive review of previous case reports with similar clinical presentations, management, and treatment of pancreatic MS.

Role of 18 F-FDG-PET/CT in an AML-M5a Subtype Patient with Rare Constellation of Hemophagocytic Lymphohistiocytosis & Bilateral Multiple Breast Chloromas

We report a treated case of acute myeloid leukemia (AML-M5a subtype) with monocytic differentiation (AMoL) presenting with fever and body pains. Initial 18 F-FDG-PET/CT ( 18 F-flurodeoxyglucose positron emission tomography/computed tomography) identified multiple lymph nodal, and marrow lesions. Biopsy confirmed hemophagocytic lymphohistiocytosis (HLH). Post HLH treatment, follow-up PET/CT demonstrated unsuspected FDG avid bilateral breast lesions ( n  = 5), which proved to be chloromas, that is, extranodal manifestation of AML. 18 F-FDG-PET/CT has helped not only in identifying the various sites of disease involvement but also in guiding the sites for biopsy. Finally, 18 F-FDG-PET/CT was useful in monitoring therapy response for both these coexisting pathologies, which are said to be resistant to treatment based on FLT3-ITD tyrosine kinase-3 internal tandem duplication mutation positivity and high-grade AML status. This case represents a rare constellation of different etiologies that needed to be differentiated. It also emphasizes the challenges in interpreting PET/CT findings, especially in difficult clinical scenarios. Disease distribution in HLH/presence of chloromas, etc., can mimic stage IV lymphoma in a known case of AML. So the nuclear medicine physician should be aware of the different complications in the background of AML, especially in patients with poor prognostic factors.

Clinicopathological analysis of CD47 and signal regulatory protein alpha expression in myeloid sarcoma patients: CD47 expression is a favourable prognostic factor

Myeloid sarcoma is a rare extramedullary haematopoietic malignancy. Interaction between CD47 and signal regulatory protein α (SIRPα) inhibits phagocytosis. CD47-positive tumours confer poor prognoses in various malignant tumours, including acute myeloid leukaemia. This study aimed to investigate the clinicopathological effects of CD47 and SIRPα expression in myeloid sarcoma. Immunohistochemistry (IHC) of CD47 and SIRPα was performed in 84 biopsy samples obtained from patients with myeloid sarcoma, some of which were CD47-positive. Patients were categorised into the following two groups based on IHC of SIRPα: those with SIRPα-positive neoplastic cells (nSIRPα) and, SIRPα expression on non-neoplastic stromal cells in tumour microenvironment (miSIRPα). In addition, patients with CD47 positivity had higher lymphocytic infiltration into the tumour microenvironment. Overall, these patients had significantly higher overall survival, however, no significant difference was observed in progression-free survival. No significant prognostic differences were observed between the nSIRPα and miSIRPα groups. This is the first study to demonstrate an association between CD47 expression and improved prognosis in myeloid sarcoma. Nonetheless, it will be necessary to conduct additional research on gene expression and genomic abnormalities to elucidate the corresponding pathogenesis of myeloid sarcoma.

Clinical characteristics, treatment options, and prognosis of myeloid sarcoma: analysis using the SEER database

BACKGROUND

Myeloid sarcoma (MS) is a very rare hematologic disorder. This study analyzes the early treatment options for patients with different types of MS and explores the prognostic factors of MS.

METHODS

Patients aged 15 years and older with MS in the SEER database (diagnosed from 2000 to 2018) were selected, excluding those with an unknown first course of treatment, an unknown location of disease, and less than 1 month of follow-up. Statistical methods used a chi-square test to compare clinical characteristics; Kaplan-Meier analysis to compare survival differences; and Cox proportional risk models to identify prognostic factors affecting overall survival (OS).

RESULTS

Data were collected from 472 patients: 244 patients with isolated myeloid sarcoma (IMS) and 228 patients with non-isolated myeloid sarcoma (non-IMS). IMS patients mostly chose local treatment, while non-IMS patients mostly chose chemotherapy. There was a significant difference in OS between IMS patients treated with combined treatment and those without treatment. For non-IMS, treated patients had longer OS than untreated, but the difference was not statistically significant. Among adult patients, those younger than 60 years had a better prognosis. Patients with the urinary system, digestive system, reproductive system and chest and abdomen as the initial site had a better prognosis.

CONCLUSIONS

Early combination therapy in IMS patients had a longer OS, and chemotherapy combined with radiotherapy/surgery should be the treatment of choice. For non-IMS patients, early combination therapy did not show a significant advantage. Age and location of first presentation were independent factors affecting MS patients' long-term prognosis.

Gastric Myeloid Sarcoma

Most gastric cancers are adenocarcinomas, but other malignancies can arise in the stomach. Patients with leukemia may develop myeloid sarcoma (MS) in the gastrointestinal tract. Our patient was a 68-year-old woman who was initially diagnosed with acute myeloid leukemia and underwent a matched unrelated stem cell transplantation. She was in remission for 10 years before developing a rare case of gastric MS without acute myeloid leukemia. She had partial response to chemotherapy but ultimately died because of infection. Gastric MS has an incidence of less than 1%. Gastrointestinal involvement usually involves the small intestine and rarely the stomach.

Myeloid sarcoma: more and less than a distinct entity

Myeloid sarcoma (MS) is a distinct entity among myeloid neoplasms defined as a tumour mass of myeloid blasts occurring at an anatomical site other than the bone marrow, in most cases concomitant with acute myeloid leukaemia (AML), rarely without bone marrow involvement. MS may also represent the blast phase of chronic myeloproliferative neoplasms (MPN) and myelodysplastic syndromes (MDS). However, the clinical and molecular heterogeneity of AML, as highlighted by the 2022 World Health Organization (WHO) and International Consensus (ICC) classifications, indirectly define MS more as a set of heterogeneous and proteiform diseases, rather than a homogeneous single entity. Diagnosis is challenging and relies mainly on histopathology, immunohistochemistry, and imaging. Molecular and cytogenetic analysis of MS tissue, particularly in isolated cases, should be performed to refine the diagnosis, and thus assign prognosis guiding treatment decisions. If feasible, systemic therapies used in AML remission induction should be employed, even in isolated MS. Role and type of consolidation therapy are not univocally acknowledged, and systemic therapies, radiotherapy, or allogeneic hematopoietic stem cell transplantation (allo-HSCT) should be considered. In the present review, we discuss recent information on MS, focusing on diagnosis, molecular findings, and treatments also considering targetable mutations by recently approved AML drugs.

Mediastinal Mass as an Initial Presentation of Acute Myeloid Leukemia in a Young Man

A 29-year-old male, hemodynamically stable, presented with chest pain radiating to the interscapular region, with no fever, cough, dyspnea, or other constitutional symptoms. He had right cervical lymphadenopathy on physical examination. Investigations revealed a 3.1 cm anterior mediastinal nodular mass, peripheral immature blood cells, and thrombocytopenia. Bone marrow core biopsy findings were consistent with acute myeloid leukemia (AML). The mediastinal mass was resected via robotic-assisted thoracoscopic surgery. Histopathology revealed involvement of the mediastinal adipose tissue with myeloid sarcoma. Molecular testing showed TP53 mutation, signifying a poor prognosis. The patient failed several lines of therapy and expired. This case demonstrates an atypical presentation of AML and emphasizes the criticality of early detection in individuals who do not exhibit the usual symptoms associated with the disease. The presence of immature cell lines in peripheral blood should prompt an investigation to determine bone marrow involvement in an otherwise healthy young adult.

Clinicopathological characteristics, genetics and prognosis of patients with myeloid sarcoma: a single-center study

AIM

Myeloid sarcoma (MS) is a rare tumour comprising myeloid blasts occurring at an anatomical site other than the bone marrow. We sought to investigate both paediatric and adult patients with MS diagnosed at our institution and determine possible correlations among their clinicopathological, phenotypic, molecular and prognostic features.

METHODS

This study retrospectively evaluated the data of 45 patients diagnosed with MS at Ege University Faculty of Medicine Hospital, Turkey, over a 17-year period.

RESULTS

The male-to-female ratio was 1.5:1, and the median age was 39.12 years. The most commonly involved sites were the skin, lymph nodes, soft tissues and bone. Immunohistochemically, CD68-KP1 was the most commonly expressed marker, followed by CD33, myeloperoxidase, CD117, lysozyme, CD68-PGM1 and CD34. Of the patients, 26 (57.7%) presented with de novo MS, 7 (15.5%) had simultaneous acute myeloid leukaemia and 12 (26.8%) had a previous history of haematological disorders. Kaplan-Meier survival analysis revealed that the 2-year and 5-year overall survival (OS) rates were 46.4% and 39.8%, respectively; the median OS duration was 11 months. Increasing age had a negative prognostic relationship with survival (p = 0.04). Chromosomal abnormalities were detected in approximately 6/10 (60%) of paediatric patients and 6/9 (66.7%) of adult patients. t(8;21)(q22;q22) translocation was identified in 20% of paediatric patients.

CONCLUSIONS

MS diagnosis is usually challenging; an expanded immunohistochemical panel should be used for an accurate diagnosis. Although MS generally has a poor prognosis, increasing age appears to be associated with a worse outcome.

RNA sequencing of myeloid sarcoma, shed light on myeloid sarcoma stratification

BACKGROUND

Myeloid sarcoma (MS) is a rare, extramedullary tumor consisting of myeloid blasts. Little is known about the genetic background of MS and the prognostic value of genetic abnormalities in MS. In particular, the broad variety of gene fusions that occur in MS is marginally covered by traditional testing methods due to lack of fresh tumor specimens.

METHODS

Here, we analyzed the clinical and genetic features of 61 MS cases. We performed RNA sequencing (RNA-seq) on formalin-fixed paraffin-embedded (FFPE) or fresh samples to analyze fusion genes in 26 cases. In addition, we performed genetic abnormalities-based risk stratification using fusion genes and gene mutations.

RESULTS

A total of 305 fusion genes were identified in 22 cases, including the following five recurrent fusion genes: RUNX1-RUNX1T1, CBFβ-MYH11, ETV6-MECOM, FUS-ERG, and PICALM-MLLT10. The prognosis in the adverse-risk group was significantly worse than that in the favorable/intermediate-risk group (median survival: 12 months vs. not reached; p = 0.0004).

CONCLUSION

These results indicated the efficacy of RNA-seq using FFPE-derived RNA as a clinical routine for detecting fusion genes, which can be used as markers for risk stratification in MS.

Intraoral myeloid sarcoma presenting as toothache and gingival mass

A female patient in her 70s with a medical history of myelodysplastic neoplasm presented to the outpatient department with a 4-month history of toothache, painful gingival swelling and loose teeth that required extractions. Intraoral examination revealed a swelling in the lower anterior portion of the mandible, which displaced her teeth. Incisional biopsy of the gingival lesion revealed dense aggregates of atypical round cells which stained positive for CD43, CD45, CD33 and myeloperoxidase, consistent with myeloid sarcoma. Subsequent bone marrow biopsy displayed hypercellular marrow with immature myeloid elements and 21% myeloblasts by flow cytometry, compatible with diagnosis of acute myeloid leukaemia (AML). The patient initially went into remission after treatment but later died of AML relapse after 18 months.

Acute Myeloid Leukemia Revealed by a Palatal Necrosis: A Rare Case Report

Acute myeloid leukemia (AML) is an aggressive hematological malignancy due to genetic alterations characterized by an overproduction of neoplastic clonal myeloid stem cells in both the bone marrow and peripheral blood. We report a case of a 43-year-old man referred to the department of hematology with a three-week history of palatal pain and weakness. The physical examination revealed an ecchymosis on the left hard palatal mucosa and necrosis. The maxillofacial computerized tomography (CT) scan revealed large osteolysis of the left maxillary bone and a fistulated soft palate. The lesion's biopsy showed an acute polymorphic inflammation with no sign of malignancy. Laboratory findings revealed anemia, thrombocytopenia, elevated lactic dehydrogenase, and elevated serum ferritin. The diagnosis was subsequently confirmed by a peripheral-blood smear revealing 60% of circulating blasts and bone marrow aspiration with 80% of blast infiltration. The latter was further classified through cytogenetic studies as an AML with deletion of chromosome 7q. This case report aims to highlight the need for clinicians to be aware of palatal necrosis as an initial manifestation of the disease and to emphasize the role of multidisciplinary collaboration between dental surgeons, oral and maxillofacial surgeons, and hematologists for early detection and treatment.

Myeloid sarcoma with ulnar nerve entrapment: A case report

BACKGROUND

Myeloid sarcoma (MS) is relatively rare, occurring mainly in the skin and lymph nodes, and MS invasion of the ulnar nerve is particularly unusual. The main aim of this article is to present a case of MS invading the brachial plexus, causing ulnar nerve entrapment syndrome, and to further clinical understanding of the possibility of MS invasion of peripheral nerves.

CASE SUMMARY

We present the case of a 46-year-old man with a 13-year history of well-treated acute nonlymphocytic leukaemia who was admitted to the hospital after presenting with numbness and pain in his left little finger. The initial diagnosis was considered a simple case of nerve entrapment disease, with magnetic resonance imaging showing slightly abnormal left brachial plexus nerve alignment with local thickening, entrapment, and high signal on compression lipid images. Due to the severity of the ulnar nerve compression, we surgically investigated and cleared the entrapment and nerve tissue hyperplasia; however, subsequent pathological biopsy results revealed evidence of MS. The patient had significant relief from his neurological symptoms, with no postoperative complications, and was referred to the haemato-oncology department for further consultation about the primary disease. This is the first report of safe treatment of ulnar nerve entrapment from MS. It is intended to inform hand surgeons that nerve entrapment may be associated with extramedullary MS, as a rare presenting feature of the disease.

CONCLUSION

MS invasion of the brachial plexus and surrounding tissues of the upper arm, resulting in ulnar nerve entrapment and degeneration with significant neurological pain and numbness in the little finger, is uncommon. Surgical treatment significantly relieved the patient’s nerve entrapment symptoms and prevented further neurological impairment. This case is reported to highlight the rare presenting features of MS.

Consolidative opacity in a patient with acute leukemia

27 year old man with newly diagnosed acute myeloid leukemia presents with new parenchymal consolidation. Although biopsy was precluded, diagnostic studies support myeloid sarcoma. Resolution of consolidation occurred with hematopoietic stem cell transplantation.

Extramedullary Infiltration in Pediatric Acute Myeloid Leukemia on Surveillance Magnetic Resonance Imaging and its Relationship With Established Risk Factors

PURPOSE

Extramedullary infiltration (EMI) is a rare condition defined by the accumulation of myeloid tumor cells beyond the bone marrow. The clinical significance is still controversial. This study was aimed to evaluate the incidence, characteristics, and prognostic significance of EMI on complete magnetic resonance imaging (MRI) investigation in newly diagnosed pediatric acute myeloid leukemia (AML) patients who are asymptomatic without clinical evidence to suspect EMI.

MATERIALS AND METHODS

Retrospective clinical and radiologic review of 121 patients with MRI examination at the time of initial diagnosis of AML without any clinical evidence suggestive of EMI was performed. Patients were divided into 2 groups according to the presence or absence of EMI, and the relationship between EMI and established risk factors was analyzed. Initial white blood cell count, the occurrence of an event (including relapse, death, and primary refractory disease), survival status, and detailed information on cytogenetic/molecular status was performed by a thorough review of electronic medical records system. All patients underwent full imaging evaluation with the contrast-enhanced whole body and some regional MRI at the time of initial diagnosis.

RESULTS

The median age at diagnosis was 10.77 years (range, 0.37 to 18.83 y). Based on the risk stratification system of AML, 36, 45, and 40 patients are classified as low-risk, intermediate-risk, and high-risk groups, respectively. MRI at the time of the initial diagnosis of AML revealed 35 of 121 patients (28.9%) with EMI. The most common site of EMI was a skull, followed by the lower extremity bone and meninges of the brain. The median age at diagnosis was significantly younger in patients with EMI (7.87 vs. 11.08 y, P=0.0212). Low incidence of FLT3/ITD mutation, low incidence of AML-ETO gene rearrangement, and the larger extent and more severe degree of bone marrow involvement was related with EMI. However, there was no significant prognostic difference in event-free survival and overall survival regardless of the presence of EMI in the overall patient population and each risk group. The location of EMI occurrence was also not related to prognosis.

CONCLUSIONS

Even if EMI symptoms are not evident, surveillance MRI scans at the initial diagnosis of pediatric AML patients are very helpful in detecting a significant number of EMIs. Younger age, some molecular features, and more severe bone marrow involvement of AML patients were related with EMI. However, there was no significant prognostic difference between patients with or without EMI regardless of risk group. Further prospective investigation is necessary to validate the prognostic effect of EMI in a larger group of patients with different risk groups.

Widespread myeloid sarcoma with KMT2A rearrangement involving the testis, oral cavity, heart, kidney and gallbladder without bone marrow involvement

Myeloid sarcoma is a solid hematological tumor consisting of growing immature myeloid cells in tissues outside the bone marrow. Myeloid sarcoma presenting before the onset of bone marrow disease is rare. Here, we report the case of a young 35-year-old male who presented with testicular mass and was diagnosed with widespread myeloid sarcoma involving internal organs like heart, kidney and gallbladder. Peripheral blood and bone marrow examination did not show any evidence of leukemia. Genetic analysis was significant for KRAS G12D mutation and KMT2A rearrangement. Induction chemotherapy for extramedullary AML with cladribine, cytarabine, GM-CSF and idarubicin (CLAG-IDA) achieved complete remission. However, the patient relapsed after 2 months and developed rapidly progressive disease. The disseminated nature of the disease in a patient without bone marrow involvement are what make this case extremely rare. Involvement of organs like heart, gall bladder and kidney is also uncommon. Isolated myeloid sarcoma is a challenge to diagnose as there are no manifestations of leukemia in peripheral blood or bone marrow, so it is usually not considered among the differential diagnoses. KM2TA rearrangement identified on genetic analysis is a rare finding in patients with AML and is associated with poor outcomes. KRAS mutations are currently being studied as therapeutic targets in these patients. This case report describes the detailed diagnostic process and discusses the possible strategies for diagnosis and treatment that can be used in similar cases.

Spine Myeloid Sarcoma: A Case Series with Review of Literature

Myeloid sarcoma (MS) is a malignant extramedullary tumor consisting of immature cells of myeloid origin. It may precede, present concurrently or follow acute myeloid leukemia (AML) in de novo case or may also be present and might be the only manifestation of recurrent AML, myelodysplastic syndrome, or chronic myeloid leukemia. It frequently involves skin, orbit, bone, periosteum, lymph nodes, and gastrointestinal tract, soft tissue, central nervous system, and testis. Because of its different localization and symptoms, and the lack of diagnostic algorithm, MS is a real diagnostic challenge particularly in patients without initial bone marrow involvement. The correct diagnosis of MS is important for optimum therapy, which is often delayed because of a high misdiagnosis rate. We reported three cases of MS derived from spine presented with back pain, paraplegia, paraparesis, respectively, and reviewed the relevant literature.

Clinicopathological analysis of myeloid sarcoma with megakaryocytic differentiation

Myeloid sarcoma (MS) is defined as a tumour mass consisting of myeloid blasts that occurs at an anatomical site other than bone marrow. MS with megakaryocytic differentiation (MSmgk) is extremely rare and its clinicopathological features have not been well described. We reviewed 11 cases in 11 patients of extramedullary mass-forming malignant tumours composed of immature non-lymphoid haematopoietic cells expressing CD41 with or without concurrent bone marrow lesions. The patients consisted of seven men and four women (1.75:1 male-to-female ratio). The mean and median ages at diagnosis were 50 and 62 years, respectively, ranging from 2 to 78 years. Extramedullary mass lesions were solitary in three cases (27%) and multiple in eight cases (73%). Tumour locations were lymph nodes (6 cases), subcutaneous tissue (3 cases), intramuscular (1 case), and bone (1 case). Seven of the 11 patients (64%) had a history of myelodysplastic syndrome (MDS) or myeloproliferative neoplasm (MPN). Three patients (27%) developed MS during remissions of acute myelogenous leukaemia, and one patient had a recurrence of MS at other sites. Follow-up data were available for four cases. Tumour cells were positive for CD41, CD33, CD34, MPO, and CD68 in 11 (100%), three (27%), seven (64%), four (36%), and seven (64%) cases, respectively. Cytogenetic analysis was successfully performed in two cases. Complex but inconsistent abnormalities were evident. When compared with cases of MS without megakaryocytic differentiation, the survival of MSmgk was significantly shorter (p=0.0033). Compared to MS without megakaryocytic differentiation, MSmgk is more likely to follow MDS/MPN, to involve multiple sites, and to be associated with poorer outcomes. More detailed studies, including genomic or gene expression analyses, could confirm the characteristics of MSmgk.

Myeloid sarcoma: an uncommon presentation of myeloid neoplasms; a case series of 4 rare cases reported in a tertiary care institute

Myeloid sarcoma (MS) is a rare extramedullary neoplasm of myeloid cells, which can arise before, concurrently with, or following hematolymphoid malignancies. We report 04 such cases of MS, diagnosed in this institute over a period of 6 years, during various phases of their respective myeloid neoplasms/leukemias. These cases include MS occurring as a relapse of AML (Case 1), MS occurring as an initial presentation of CML (Case 2), MS occurring during ongoing chemotherapy in APML (Case 3), and MS presenting as a progression of MDS to AML (Case 4). In the absence of relevant clinical history and unemployment of appropriate immunohistochemical (IHC) studies, these cases have a high risk of being frequently misdiagnosed either as Non-Hodgkin’s Lymphoma (NHL) or small round cell tumors or undifferentiated carcinomas, which may further delay their management, making an already bad prognosis worse. This case series has been designed to throw light on the varied presentation of MS and the lineage differentiation of its neoplastic cells through the application of relevant IHC markers along with their clinical correlation.

Gastrointestinal Myeloid Sarcoma a Case Presentation and Review of the Literature

Myeloid sarcomas can be detected in up to 30% of acute myeloid leukemia cases or occur de-novo without bone marrow involvement. The most frequent localization of myeloid sarcomas in the abdominal cavity is the small intestine, and gastric presentations are infrequent, frequently misdiagnosed, and a high level of suspicion should exist when the characteristic histomorphology features are present. The current review features a case report with gastric presentation of myeloid sarcoma in a patient with a diagnosis of acute myeloid leukemia with trisomy 8. In addition, a review of the literature of intestinal-type myeloid sarcomas shows that less than 15% of these cases have been reported in the stomach. The most common molecular aberrancy detected in intestinal myeloid sarcomas is the fusion protein CBFB-MYH11. A review of several large studies demonstrates that the presence of myeloid sarcoma does not constitute an independent prognostic factor. The therapeutic approach will be tailored to the specific genetic abnormalities present, and systemic chemotherapy with hematopoietic stem cell transplant is the most efficient strategy.

FDG-PET/CT Variants and Pitfalls in Haematological Malignancies

Hematologic malignancies represent a vast group of hematopoietic and lymphoid cancers that typically involve the blood, the bone marrow, and the lymphatic organs. Due to extensive research and well defined and standardized response criteria, the role of [¹⁸F]FDG-PET/CT is well defined in these malignancies. Never the less, the reliability of visual and quantitative interpretation of PET/CT may be impaired by several factors including inconsistent scanning protocols and image reconstruction methods. Furthermore, the uptake of [¹⁸F]FDG not only reflects tissue glucose consumption by malignant lesions, but also in other situations such as in inflammatory lesions, local and systemic infections, benign tumors, reactive thymic hyperplasia, histiocytic infiltration, among others; or following granulocyte colony stimulating factors therapy, radiation therapy, chemotherapy or surgical interventions, all of which are a potential source of false-positive or negative interpretations. Therefore it is of paramount importance for the Nuclear Medicine Physician to be familiar with, not only the normal distribution of [¹⁸F]FDG in the body, but also with the most frequent findings that may hamper a correct interpretation of the scan, which could ultimately alter the patients management. In this review, we describe these myriad of situations so the interpreting physician can be familiar with them, providing tools for their correct identification and interpretation when possible.

Single Fraction Radiation for Myeloid Sarcoma Is as Effective as Multi-Fraction Regimens for Tumor Regression and Control

INTRODUCTION/BACKGROUND

Myeloid sarcoma is a rare extramedullary manifestation of immature myeloid/monocyte cells. Radiotherapy (RT) yields good local control, but data on different fractionation schemes are limited. The goal of this retrospective study was to share our institutional experience and assess volumetric regression with differential fractionation.

MATERIALS AND METHODS

We evaluated patients treated for myeloid sarcoma between 2000 and 2019 and categorized them into Group A (treated with RT) and Group B (no RT). We assessed local control using cumulative incidence function analysis. Post-treatment imaging sequences were analyzed for volumetric calculations.

RESULTS

Forty-four patients with 80 lesions were assessed. Twenty-three patients with 52 lesions received RT (Group A), and 6 lesions received a single fraction of RT. There were 2 instances of local progression in Group A and 8 in Group B, with a cumulative incidence function estimate of local progression in Group A of 2.4% at 1 year and 6.9% at 2 years, significantly reduced compared to 29.7% and 35.5% in Group B, respectively (hazard ratio 0.13 [95% confidence interval 0.030.63], P = .011). No lesion treated with a single fraction of RT developed local progression. Volumetric analysis for 19 chronologically followed lesions (including 3 treated with a single fraction) revealed no difference in regression between single or multi-fraction treatment.

CONCLUSION

RT for myeloid sarcoma yields excellent local control and may be as effective in a single fraction as more protracted courses, though this requires validation. For a diagnosis associated with poor survival, a single palliative fraction may be optimal with potential for higher utilization.

Oral myeloid sarcoma as an uncommon manifestation of acute myeloid leukemia: A case series and review of the literature

BACKGROUND AND OVERVIEW

Oral myeloid sarcoma (MS) is an extramedullary tumor that can occur in the setting of acute myeloid leukemia, either as the first sign of an underlying disease or later in the course of disease. The authors' aim was to present the clinical features of oral MS and review the literature.

CASE DESCRIPTION

Case 1 was an 82-year-old woman with an asymptomatic erythematous swelling on the maxillary gingiva and no history of hematologic malignancy. Case 2, a 65-year-old man, and case 3, a 58-year-old woman, each had a history of acute myeloid leukemia and a painful ulcer on the palatal mucosa and an asymptomatic ulcer on the lower lip mucosa, respectively. Case 1 was treated with focal radiation then chemotherapy and achieved complete remission initially, but died of relapse 2 years after diagnosis. Case 2 received radiotherapy and immunotherapy and had a complete response. Case 3 received chemotherapy and achieved remission initially, but relapsed and is undergoing investigational targeted therapies.

CONCLUSIONS AND PRACTICAL IMPLICATIONS

Oral MS can manifest as gingival or mucosal swelling or ulceration and can indicate onset or relapse of associated hematologic malignancies, which often have a poor prognosis. Because patients with oral findings are likely to seek treatment from their dentists first, oral clinicians should maintain a broad differential diagnosis list when evaluating oral lesions, especially if treatment prescribed for a more common diagnosis fails to resolve the lesion.

Granulocytic Sarcoma: A Rare Cause of Wrist Pain

Septic, inflammatory, or crystal-induced arthritis are common etiologies of wrist pain without antecedent trauma associated with pain, loss of motion, swelling, redness, and warmth. In this report, we detail the case of granulocytic sarcoma of the wrist that presented as acute wrist pain, swelling, and limitation in motion. Granulocytic sarcoma is an exceedingly rare extramedullary tumor associated with acute myeloblastic leukemia. It may be found in any part of the body; however, upper extremity involvement is uncommon. To our knowledge, this is the first description of granulocytic sarcoma occurring in the wrist joint.

The myeloid sarcoma treated by Venetoclax with hypomethylating agent followed by stem cell transplantation: rare case report

BACKGROUND

Myeloid sarcoma (MS) is a very rare condition, develops both in patients with other hematological neoplasms, and as isolated tumor. MS of the gynecologic tract is extremely rare. An available literature data about diagnosis and management of MS is summarized in the article. The role of chemotherapy, radiation therapy, surgery and bone marrow transplantation in the treatment is discussed. Polychemotherapy and allogeneic bone marrow transplantation were suggested to be the optimal treatment strategy of MS of the gynecological tract. The use of new targeted agents results in promising clinical data.

CASE PRESENTATION

We are presenting a rare clinical case of a MS of the uterine cervix with concomitant bone marrow involvement and describe all the peculiarities of the clinical course, diagnosis, and treatment. The patient received chemotherapy followed by allogeneic bone marrow transplantation. The pre-transplant therapy allowed us to perform allogeneic bone marrow transplantation with the deepest response possible: complete PET-negative and MRD-negative remission of the disease.

CONCLUSIONS

MS remains a subject of discussion regarding its diagnostic and therapeutic aspects. The use of novel targeting agents can be perspective option for patient with extramedullary disease.

Epidemiological evaluation and survival of children with acute myeloid leukemia

OBJECTIVE

This study aims to describe the epidemiological characteristics and survival rates of children with acute myeloid leukemia treated in hospitals in southern Brazil and compare them with international data.

METHODS

A multicenter cohort study was conducted with retrospective data collection of all new patients with acute myeloid leukemia under 18 treated at five referral centers in pediatric hematology-oncology in southern Brazil between January 2005 and December 2015.

RESULTS

Of the 149 patients with acute myeloid leukemia, 63.0% (n=94) were male. The median age at diagnosis was 10.5 years (range 0-18 years) and 40.3% (n=60) had a white blood cell count below 50,000/mm². The most common Franco-American-British (FAB) subtype was M3 (n=43, 28.9%). Nine (6.0%) patients had central nervous system disease. In M3 patients, overall survival (OS) was 69.2% and 3-year event-free survival was 67.7%; in non-M3 patients, these rates were 45.3% and 36.7%, respectively. In non-M3 patients, OS was significantly different between transplanted (61.8%) and non-transplanted (38.2%) patients (p=0.031).

CONCLUSIONS

These results show a higher prevalence of the Franco-American-British M3 subtype than that reported in the international literature, as well as a decreased OS compared with that of developed countries. Further multicenter Brazilian studies with a larger sample size are encouraged to better understand the characteristics of acute myeloid leukemia, and to improve the treatment and prognosis in this population.

Diagnosis and surgical treatment of primary isolated aggressive lumbar myeloid sarcoma: a rare case report and review of the literatures

BACKGROUND

Myeloid sarcoma is a rare, extramedullary, solid tumor derived from immature myeloid cell precursors. It is most frequently accompanied by acute myelogenous leukemia, though infrequently found in non-acute myelogenous leukemia patients. The tumor may involve any part of the body, but the lumbar spine is seldom involved. The present case study aims to understand the diagnosis and surgical treatment of a rare primary isolated myeloid sarcoma of the lumbar spine causing aggressive spinal cord compression in a non-acute myelogenous leukemia patient.

CASE PRESENTATION

A 29-year-old man complained of an aggressive radiating pain to the lower extremities and moderate dysuria with a Visual Analogue Scale score that gradually increased from 3 to 8. Lumbar enhanced magnetic resonance imaging and computed tomography revealed a lumbar canal lesion at lumbar spine L2 to L4 with spinal cord compression. A whole body bone scan with fused single photon emission computed tomography/computed tomography demonstrated abnormal ^99mTc-methylene diphosphonate accumulation in the L3 lamina and spinous process. No evidence of infection or hematology disease was observed in laboratory tests. Due to rapid progression of the symptoms and lack of a clear diagnosis, decompression surgery was performed immediately. During the operation, an approximately 6.0 × 2.5 × 1.2 cm monolithic, fusiform, soft mass in the epidural space and associated lesion tissues were completely resected. The radiating pain was relieved immediately and the dysuria disappeared within 1 week. Intraoperative pathological frozen section analysis revealed a hematopoietic malignant tumor and postoperative immunohistochemistry examination confirmed the diagnosis of myeloid sarcoma.

CONCLUSIONS

The primary isolated aggressive lumbar myeloid sarcoma is rarely seen, the specific symptoms and related medical history are unclear. Surgery and hematological treatment are effective for understanding and recognizing this rare tumor.

Rare presentation of isolated bilateral testicular myeloid sarcoma: A case report

Myeloid sarcoma (MS) of the testis is a rare soft tissue tumour which can herald the development of acute myeloid leukaemia (AML). The diagnosis of MS requires a high degree of suspicion as appropriate immunohistochemical staining must be performed to yield an early diagnosis. Whilst there is no consensus on treatment on MS involving the testis, most patients undergo orchidectomy and systemic chemotherapy, with or without radiation therapy. Early and aggressive treatment is key to achieving remission.

This case report describes a patient with bilateral testicular MS which heralded the development of AML, who underwent induction chemotherapy and achieved remission.

Genomic analysis in myeloid sarcoma and comparison with paired acute myeloid leukemia

Myeloid sarcoma (MS) is a rare manifestation of acute myeloid leukemia (AML) characterized by extramedullary proliferation of myeloid blasts. Owing to the rarity of MS, the clonal evolution of cell populations giving rise to MS is not well understood. To study the genomic signature of MS, we used a capture-based next-generation sequencing panel targeting 479 cancer genes to interrogate the genetic variants present in MS samples and compared their genetic profiles with their paired AML samples from a cohort of seven individuals. We identified a spectrum of single-nucleotide variants (SNVs) and a spectrum of copy number alterations in MS. Our study found that variant profiles observed in MS were generally similar to AML from the same individual, supporting the notion that these tumors are derived from a common precursor, rather than de novo tumors in a susceptible host. In addition, MS cases with a higher number of SNVs show worse clinical outcomes than MS with a lower number of SNVs. Identification of these abnormalities could potentially contribute to improved prognostic classification and identify new therapeutic targets for MS.

Myeloid sarcoma, chloroma, or extramedullary acute myeloid leukemia tumor: A tale of misnomers, controversy and the unresolved

The World Health Organization classification and definition of "myeloid sarcoma" is imprecise and misleading. A more accurate term is "extramedullary acute myeloid leukemia tumor (eAML)." The pathogenesis of eAML has been associated with aberrancy of cellular adhesion molecules, chemokine receptors/ligands and RAS-MAPK/ERK signaling. eAML can present with or without synchronous or metachronous intramedullary acute myeloid leukemia (AML) so a bone marrow evaluation is always recommended. Accurate diagnosis of eAML requires tissue biopsy. eAML confined to one or a few sites is frequently treated with local therapy such as radiotherapy. About 75-90% of patients with isolated eAML will develop metachronous intramedullary AML with a median latency period ranging from 4 to 12 months; thus, patients with isolated eAML may also be treated with systemic anti-leukemia therapy. eAML does not appear to have an independent prognostic impact; selection of post-remission therapy including allogeneic hematopoietic cell transplant (alloHCT) is typically guided by intramedullary disease risk. Management of isolated eAML should be individualized based on patient characteristics as well as eAML location and cytogenetic/molecular features. The role of PET/CT in eAML is also currently being elucidated. Improving outcomes of patients with eAML requires further knowledge of its etiology and mechanism(s) as well as therapeutic approaches beyond conventional chemotherapy, ideally in the context of controlled trials.

Extramedullary Acute Myeloid Leukemia of the Renal Pelvis: Insights into a Visceral Niche

Acute myeloid leukemia (AML) is a stem cell malignancy that originates in the bone marrow and involves the peripheral blood. Extramedullary AML is rarer, but it is most commonly associated with the former French-American-British (FAB) subtypes M4 or M5 of AML. AML cells may also home to the central nervous system and other solid organs such as cortical bone and skin. Such target sites of metastasis depend on microenvironmental niche interactions, which have not been fully elucidated to date. Visceral organs usually do not represent a favorable niche for AML stem cell occupancy. Herein, we describe the case of an 80-year-old man with extramedullary AML involvement of the renal pelvis. Hypercalcemia and obstructive uropathy were presenting features. The visceral niche is a rare site of involvement of myeloid malignancy, and hypercalcemia may reflect a mechanism of extramedullary involvement. We propose a treatment paradigm for this uncommon subset of AML based on advanced age and complex karyotype.

Myeloid sarcoma of the nasal cavity in a 15-month-old child: A case report

INTRODUCTION

Myeloid sarcoma (MS) is a rare tumor mass. It may occur at any extramedullary anatomic sites but is uncommon in the sinonasal location.MS commonly presents concurrently with acute myeloid leukemia (AML), but it may predate AML over several months or years, named isolated MS.

PATIENT CONCERNS

We report a case of a 15-month-old child who presented with mouth breathing, bilateral rhinorrhea, palpebral edema and proptosis. The routine blood tests were normal for the first few months. Computed tomography scan revealed neoplasm in nasal cavity.

DIAGNOSIS

The patient was definitely diagnosed with isolated MS in the nasal cavity through immunohistochemistry combined with clinical features and radiological investigations, and MS further progressed to AML which was confirmed by hematologist.

INTERVENTIONS

Endoscopic sinus surgery was performed to acquire specimens. After diagnosis, the patient was promptly treated with systemic chemotherapy.

OUTCOMES

All symptoms gradually subsided and the mass of nasal cavity was invisible. No relapse occurred during follow-up.

CONCLUSION

Sinonasal MS may be misdiagnosed and should be considered when symptoms persist and worsen. Prompt clinic examinations are essential for cases with suspected MS. Diagnosis of MS is dependent on the immunohistological investigations combined with clinical features, radiological investigations. Early diagnosis and systemic chemotherapy are vital for patients to achieve best prognosis.

Diagnostic and Therapeutic Considerations for Extramedullary Leukemia

PURPOSE OF REVIEW

The purpose of this review is to summarize the current literature on the presentation, diagnosis, and treatment options available for extramedullary (EM) manifestations of leukemia including myeloid sarcoma (MS) and leukemia cutis (LC).

RECENT FINDINGS

Advanced imaging using 18FDG-PET/CT is an effective screening tool for EM manifestations of leukemia. The role of radiation therapy has been more clearly delineated in the treatment of both MS and LC. FDA-approved targeted agents have improved outcomes in patients with AML but have not demonstrated improvements specifically for EM; however, a checkpoint inhibitor, Ipilimumab, holds promise in impacting local control for the treatment of AML-related EM. EM manifestations of leukemia pose significant therapeutic challenges. Treatment of EM is predicated on multiple factors including the presence of concomitant bone marrow involvement, AML-risk classification, and timing of presentation at initial diagnosis or relapse following systemic therapy.

Granulocytic/myeloid sarcoma with trisomy 21 presented as an epididymal tumor: A case report and review of the literature

Myeloid sarcoma is an extramedullary tumor composed of immature myeloid cells and occurs in various extramedullary sites. We report a 48-year-old man diagnosed with myeloid sarcoma in the epididymis. He was admitted to our hospital due to a painless right intrascrotal mass. Magnetic resonance imaging showed a 30 mm tumor in the right epididymis, and we subsequently performed right high orchiectomy. The pathological diagnosis was myeloid sarcoma. Bone marrow aspiration and biopsy revealed no hematological disease, and cytogenetic analysis in the bone marrow showed normal karyotype. He was diagnosed with isolated myeloid sarcoma in the epididymis. Six months after the operation, myeloid sarcoma recurred in the para aorta and left sub-diaphragm. Bone marrow examination revealed myelodysplastic syndrome, and cytogenetic analysis showed 46, XY. We performed surgical resection of the recurrent mass, and cytogenetic analysis showed 47, XY, +21. He was diagnosed with recurrent MS with adult-onset trisomy 21. Although the effect of trisomy 21 on prognosis is unknown, the patient is currently undergoing systemic chemotherapy with maintained remission.

Bilateral ovarian granulocytic sarcoma as the primary manifestation of acute myelogenous leukemia treated with allogenic stem cell transplantation: A case report

RATIONALE

Granulocytic sarcoma (GS), also known as chloroma, is a tumor comprising myeloblasts or monoblasts, potentially occurring as an extramedullary mass. Systemic chemotherapy should be used to induce complete remission. However, such patients with chloroma have a poorer treatment outcome than those without extramedullary myeloid sarcomas.

PATIENT CONCERNS

A 30-year-old woman who initially presented with bilateral ovarian masses and splenomegaly was admitted to hospital. Also, her complete blood cell counts showed pancytopenia and blood smear revealed a few immature cells (3%).

DIAGNOSES

A bone marrow biopsy demonstrated acute myelomonocytic leukemia, and the chromosomal analysis revealed a 46, XX, del18 (p11) [20] karyotype and cytogenetics and molecular markers showed all negative results.

INTERVENTIONS

Since this diagnosis, she received remission-inducing chemotherapy comprising anthracycline and cytarabine, which is a standard regimen for acute myeloid leukemia (AML), and followed by allogenic hematopoietic stem cell transplantation from Human leukocyte antigen (HLA)-identical sibling donor.

OUTCOMES

After transplantation, the bone marrow engrafted successfully without complications. She visited our clinic regularly with no evidence of leukemia relapse or graft-versus host disease.

LESSONS

This report represents the first case of ovarian GS, wherein treatment was successful with high-dose chemotherapy, followed by allogenic hematopoietic stem cell transplantation without oophorectomy.

Vulvar myeloid sarcoma as the presenting symptom of acute myeloid leukemia: a case report and literature review of Chinese patients, 1999-2018

BACKGROUND

Myeloid sarcoma (MS), which represents a rare malignancy that comprises of myeloid blasts occurring at extra-medullary sites, closely correlates with the onset and relapse of acute myeloid leukemia (AML) and other hemopoietic neoplasm. Female genital system is an uncommon location of MS, with the vulvar MS being even rarer that only eight cases have been reported in English-written literature.

CASE PRESENTATION

A 47-year-old woman presented with chronic ulceration on her vulva for one and a half month. Microscopic examination of incisional biopsy revealed dermal infiltration of myeloid precursor cells, which were positive for MPO, lysozyme, CD43, CD68, CD38 and CD117. Bone marrow flowcytometric analysis showed myeloblast count of 74%, which expressed CD13, CD33, CD117 and HLA-DR. A diagnosis of AML (M2 type) was made and vulvar MS was the earliest symptom. The patient achieved complete remission after chemotherapy with no evidence of recurrence in a 27-month follow-up. We reviewed the literature and identified 54 cases of Chinese patients with gynecological MS between 1999 and 2018, and discovered that in Chinese population, MS most frequently involved uterine cervix followed by the ovary and vulva, and ovarian MS onset much earlier than other sites. Remarkably, vulvar MS exhibited a high rate of concurrent AML and secondary myeloid leukemia within a short time of its occurrence. Despite its limited distribution, MS should be tackled aggressively with chemotherapy followed by allogeneic hematopoietic stem cell transplantation if the appropriate donor is available.

CONCLUSIONS

Female genital MS, especially vulvar MS, should be included in the differential diagnosis of gynecological neoplasm, which will facilitate its early diagnosis and prompt management.

Challenges associated with limited-resources cancer care facility: Bilateral breast myeloid sarcoma as an example

Myeloid sarcoma (MS) is a rare myeloid malignancy. It can arise before, concurrent with, or following different malignant hematological diseases, most commonly acute myeloid leukemia (AML), myelodysplastic syndrome, or myeloproliferative neoplasms. Here we describe a 30-year-old female with AML-M1 who presented to the hematology department with bilateral breast pain and tenderness. Available diagnostic measures including ultrasound of breast and magnetic resonance imaging were used to determine the nature of these breast lumps. MS was definitively diagnosed via biopsy and the patient was treated with systemic chemotherapy. Despite her AML treatment she unfortunately died secondary to disease progression. The authors consider this case of particular educational value due to the bilateral and aggressive nature of this patient's disease in the setting of a cancer-care facility with limited resources.

KEY CLINICAL MESSAGE

In retrospect, if breast MS had been considered earlier in this patient's presentation, a referral to an outside center with matched stem cell transplantation capability may have been warranted after complete remission following first bone marrow relapse, rather than continuing chemotherapy alone.

Myeloid sarcoma manifesting as generalized lymphadenopathy in a patient with myelofibrosis

Immunophenotyping is critical to the diagnosis of MS, as it can be difficult to differentiate from other diagnoses including lymphoma using conventional light microscopy.

[Lung involvement in hematologic systemic diseases]

Pulmonary diseases can occur across the entire disease spectrum of malignant hematologic systemic diseases. Although infectious processes of the lungs are common in these immunosuppressed patient collectives, noninfectious causes account for up to half of the pulmonary manifestations found in hematologic malignancies. Besides the frequent infections including opportunistic pathogens, a broad differential diagnosis including drug-induced lung injury by cytostatic substances, cytokines, and innovative immunotherapeutic agents, rarer transfusion of blood products and intrathoracic manifestations of the hematologic malignancy itself, have to be kept in mind. Finally, vascular complications can also lead to pulmonary reactions. Early and consistent diagnostics and treatment of the bronchopulmonary, intrathoracic and vascular complications within the framwework of hematologic systemic diseases can be essential for the patient's prognosis.

Cardiac chloroma or cardiac myeloid sarcoma: Case Report

Chloroma or myeloid sarcoma is rare extramedullary tumor composed of immature myeloid cells that may occur in association with or during or even before the course of adult myelodysplastic or myeloproliferative diseases. It may involve different organs including the orbit, skin, lymph nodes, bone, gastrointestinal tract, breast, central nervous system, and lung. Cardiac involvement with MS is an exceedingly rare finding. We report a very rare case of left ventricular cardiac chloroma accidentally discovered by transthoracic echocardiography (TTE) and confirmed by cardiac magnetic resonance (CMR) in an old aged male patient with acute myeloid leukemia (AML) French-American-British (FAB)-class M5. Unfortunately, shortly after a prompt start of AML palliative chemotherapy protocols, the patient died due to massive intracranial hemorrhage (ICH).

Neuroleukemiosis: Diagnosis and management

An exceedingly rare manifestation of leukemia, termed neuroleukemiosis, involves peripheral nerve infiltration by leukemic cells. Patients with neuroleukemiosis typically present with a peripheral neuropathy and/or chloromatous masses. The diagnosis is supported by, and established with, electrophysiologic testing, imaging, histopathology, and immunophenotyping. We present the case of 21 year old male with multiply relapsed M4 type of acute myelogenous leukemia (AML) who presented with extremity pain and was subsequently found to have multiple cervical, thoracic, and lumbosacral nerve root masses. A diagnosis of neuroleukemiosis was established via CT-guided biopsy and immunophenotyping. The patient's neuroleukemiosis responded well to chemotherapy, donor lymphocyte infusions, and spinal irradiation. The literature is reviewed regarding this interesting and rare clinical condition.

Clinical characteristics and management of primary granulocytic sarcoma of the breast: A case report

RATIONALE

Primary granulocytic sarcoma of the breast is a rare and poor-prognosis malignancy. Clinicians do not have sufficient knowledge of this disease and often misdirect it as other soft tissue sarcomas or inflammation.

PATIENT CONCERNS

A 42-year-old female presented with a self-discovered asymptomatic growing and palpable right breast mass that had been present for 4 months.

DIAGNOSES

The patient was diagnosed as primary myeloid sarcoma.

INTERVENTIONS

The patient received modified radical mastectomy in the right breast and sentinel lymph node biopsy. Pathological diagnosis is primary granulocytic sarcoma. Then the patient accepted acute myeloid leukemia-induction chemotherapy.

OUTCOMES

The follow-up of this patient has no evidence of disease progression or spread during 1 year.

LESSONS

Granulocytic sarcoma in the breast tissue is rare. But it still should be considered in the differential diagnosis of any tumor in the breast. The present study discusses comprehensively the clinical and pathological characteristics to improve the understanding of myeloid sarcoma.

Myeloid sarcoma presenting as bilateral acute otitis externa in newly diagnosed acute myeloid leukemia

Myeloid sarcoma (MS) is an extramedullary collection of immature myeloid cells that can commonly occur with acute myeloid leukemia (AML). While head and neck presentations are not unheard of, there have been few published pediatric cases of external auditory canal MS. Here, we report a case of a 14-year-old male who presented with MS masquerading as bilateral acute otitis externa. To the best of our knowledge, this is the first reported case of a bilateral presentation leading to a new diagnosis of AML. A literature review of head and neck presentations of MS is included.

Testicular Myeloid Sarcoma: A Systematic Review of the Literature

Myeloid sarcoma usually involves lymph nodes, and head and neck regions. Uncommon sites like testis and ovary are rarely involved and pose a diagnostic challenge. Nonspecific findings, difficulty in retrieving biopsy specimens, and associated infertility are few of the hurdles faced during diagnosis and treatment of testicular myeloid sarcoma. Our review is an attempt to study myeloid sarcoma involving testis.

Clinical and Radiographic Response of Extramedullary Leukemia in Patients Treated With Gemtuzumab Ozogamicin

Extramedullary leukemia (EML) is common in pediatric acute leukemia and can present at diagnosis or relapse. CD33 is detected on the surface of myeloid blasts in many patients with acute myelogenous leukemia and is the target of the antibody drug conjugate gemtuzumab ozogamicin (GO). Here we present 2 patients with CD33 EML treated with GO. They achieved significant response, with reduction of EML on both clinical and radiographic exams, specifically fluorine fluorodeoxyglucose positron emission tomography/computed tomography, demonstrating potential for targeted therapy with GO as a means of treating EML in patients with CD33 leukemia and the utility of fluorine fluorodeoxyglucose positron emission tomography/computed tomography monitoring in EML.