Myeloid sarcoma (MS) represents a neoplastic proliferation characterized by immature myeloid precursor cells. Among its variants, aleukemic MS is an uncommon subtype, manifesting as skin involvement sparing the peripheral blood or bone marrow. The non-specific cutaneous presentation coupled with the lack of associated symptoms poses a diagnostic challenge for providers. In this report, we present a case of an 83-year-old woman who presented with violaceous nodules located in the center of her right shin. A biopsy of the lesion unveiled a diagnosis of MS, yet notably lacked peripheral blood involvement. Three months after the initial diagnosis, the MS was found in the common bile duct, still without bone marrow involvement. With a relatively poor prognosis, the rapid diagnosis and treatment of MS are crucial.

Myeloid sarcoma (MS) occurs in patients with acute myeloid leukemia (AML). In rare cases, MS can represent a form of blast transformation in patients with myeloproliferative neoplasms (MPN), myelodysplastic neoplasms (MDS), or MDS/MPN. The most frequent chromosomal alterations in MS are t(8;21) or inv(16), with other alterations being reported. Cases of MS in Janus kinase 2 (JAK2)-positive MDS with fibrosis are exceedingly rare. Here, we describe such a case. To the best of our knowledge, this is the first report of a JAK2 V617F mutation-positive MDS case occurring concurrently with MS involving the posterior aspect of the left seventh rib. No clear association has been previously demonstrated between the intramedullary AML cytogenetics and extramedullary disease occurrence. Interestingly, samples from the intramedullary MDS and extramedullary mass in this patient presented the same JAK2 V617F mutation. Following a treatment regimen of azacitidine and venetoclax, the patient achieved complete remission. The chest CT scan showed that the seventh posterior rib mass disappeared. This case provides valuable information for the potential future treatment of this disease.

BACKGROUND: Myeloid sarcoma (MS), also referred to as granulocytic sarcoma or chloroma, is a rare type of extramedullary malignant tumor. MS comprises primitive granulocytic precursor cells that play a key role in the early stages of white blood cell development. Notably, the occurrence of this tumor in the gingiva is rare.
METHODS: The present study reported the case of MS with gingival swelling in the maxillary region, with aleukemic presentation in a 32-year-old male patient. Following two courses of chemotherapy, computed tomography of the region demonstrated complete clearance of the tumor. At the 12-month follow-up appointment, the patient was in a stable condition with the absence of progression. The etiology, clinical features, diagnosis, and relevant treatment of MS are discussed in the present study.
CONCLUSIONS: Diagnosis of MS may be confirmed following histological and immunohistochemical examinations.

Myeloid sarcoma, a rare extramedullary manifestation of acute myeloid leukemia (AML), can occur in various anatomic sites but seldom involves the gastrointestinal tract. We report the unusual case of a 49-year-old man with a history of AML who initially presented with abdominal pain and imaging findings suggestive of a paracolic abscess. However, the lesion rapidly progressed to a large descending colon mass with peritoneal involvement over five weeks. Surgical resection and histopathological examination confirmed a diagnosis of myeloid sarcoma. This case highlights the potential of myeloid sarcoma to mimic an inflammatory colonic process at initial presentation prior to manifesting as an overt mass lesion. Although exceedingly rare, myeloid sarcoma should be considered in patients with a history of AML presenting with colon lesions, particularly in those with an aggressive clinical course. Early recognition may expedite appropriate treatment and prevent unnecessary procedures. This report also underscores the importance of correlating imaging findings with clinical history and histopathology findings to establish an accurate diagnosis.

The classification of clonal plasmacytoid dendritic cell (pDC) proliferation associated with myeloid neoplasms remains a topic of ongoing debate. Although the fifth edition of the World Health Organization classification classifies clonal pDC proliferation into two categories, it is unclear whether this classification adequately captures the complexities of clonal pDC pathogenesis. We present a clinical case featuring myeloid sarcoma with pDC-like cells in cervical lymph nodes and bone marrow (BM). Analysis of biopsy specimens and BM aspirate revealed two distinct cellular populations expressing myeloid and pDC markers. One population exhibited myeloid leukemia and monocyte markers, including MPO, CD13, CD33, CD11b, and CD14, while the other manifested an immunophenotype reminiscent of pDCs, characterized by expression of CD56 and CD123. Additionally, whole exome sequencing and RNA sequencing of BM mononuclear cells were conducted to explore the pathophysiology of this rare malignancy, and unveiled pDC-like cell proliferation driven by IKZF1 and ETV6 mutations originating from clonal hematopoiesis initiated by a DNMT3A mutation. Notably, venetoclax-based therapy exhibited efficacy for achieving and sustaining complete remission. This case provides pivotal insights into the mechanistic aspects of pDC/pDC-like cell proliferation in myeloid sarcoma, offering valuable perspectives on therapeutic strategies.

Myeloid sarcoma (MS) is a solid tumor of granulocytic origin with extramedullary localization. This tumor is rare in humans and animals. The diagnostic approach is heterogeneous, and the definitive diagnosis may be difficult to achieve. Primary MS has never been described as a spontaneous neoplasm in companion dogs. Two purebred and 1 mixed-breed dogs, 6- to 11-year-old, developed round cell tumors in the mediastinum, lymph nodes (LNs) and tonsils, and LNs, respectively. Granulocytic origin and exclusion of lymphoid lineage were confirmed by flow cytometry, supported by immunohistochemistry or immunocytochemistry. Pivotal to the diagnosis were positive labeling for myeloid (CD11b, CD14) and hematopoietic precursors (CD34) markers, along with negative labeling for lymphoid markers. Blood and bone marrow infiltration were not detected at initial diagnosis, excluding acute myeloid leukemia. The behavior of these tumors was aggressive, resulting in poor clinical outcomes, even when chemotherapy was attempted.

UNASSIGNED: Acute promyelocytic leukemia (APL) is rarely caused by the PLZF::RARα fusion gene. While APL patients with PLZF::RARα fusion commonly exhibit diverse hematologic symptoms, the presentation of myeloid sarcoma (MS) as an initial manifestation is infrequent.
UNASSIGNED: A 61-year-old patient was referred to our hospital with 6-month history of low back pain and difficulty walking. Before this admission, spine magnetic resonance imaging (MRI) conducted at another hospital revealed multiple abnormal signals in the left iliac bone and vertebral bodies spanning the thoracic (T11-T12), lumbar (L1-L4), and sacral (S1/S3) regions. This led to a provisional diagnosis of bone tumors with an unknown cause. On admission, complete blood count (CBC) test and peripheral blood smear revealed a slightly increased counts of monocytes. Immunohistochemical staining of both spinal and bone marrow (BM) biopsy revealed positive expression for CD117, myeloperoxidase (MPO), and lysozyme. BM aspirate showed a significant elevation in the percentage of promyelocytes (21%), which were morphologically characterized by round nuclei and hypergranular cytoplasm. Multiparameter flow cytometry of BM aspirate revealed that blasts were positive for CD13, CD33, CD117, and MPO. Through the integrated application of chromosome analysis, fluorescence in situ hybridization (FISH), reverse transcriptase polymerase chain reaction (RT-PCR), and Sanger sequencing, it was determined that the patient possessed a normal karyotype and a rare cryptic PLZF::RARα fusion gene, confirming the diagnosis of APL.
UNASSIGNED: In the present study, we report the clinical features and outcome of a rare APL patient characterized by a cryptic PLZF::RARα fusion and spinal myeloid sarcoma (MS) as the initial presenting symptom. Our study not only offers valuable insights into the heterogeneity of APL clinical manifestations but also emphasizes the crucial need to promptly consider the potential link between APL and MS for ensuring a timely diagnosis and personalized treatments.

BACKGROUND: The treatment of myeloid sarcoma (MS) is challenging and has not markedly improved patient prognosis. The introduction of venetoclax (VEN) has changed the treatment of MS, and venetoclax-based therapy has been described as very promising in several case reports.
METHODS: In this retrospective study, we analyzed the treatment outcomes of 14 patients with MS treated with venetoclax-based therapy at The First Affiliated Hospital of Xiamen University from January 2020 to October 2023 RESULTS: The cohort consisted of 7 (50%) women and 7 (50%) men with an average age of 37.5 years. Four patients (28.6%) had isolated MS de novo, 2 (14.2%) were diagnosed synchronously with AML, and 8 (57.2%) had isolated extramedullary relapse. The most common sites for MS in our cohort were the skin and lung, followed by the spinal canal, soft tissue, bone and kidney. Five patients were affected at more than three sites. Nine patients received VEN in combination with azacytidine, and 5 patients received VEN in combination with other agents. The median number of venetoclax therapies administered was 2 cycles (range: 1-10 cycles). A response was observed in all patients included in the study, with 8 patients (57.2%) achieving a CR and 3 patients (21.4%) achieving a PR, corresponding to an ORR (including CR and PR) of 78.6%. The median follow-up time for all patients was 13 months (range 1-44 months), and the 1 year OS for all patients was 67.7%.
CONCLUSIONS: Venetoclax-based therapy shows excellent efficacy and safety in MS patients in the \"real world\" at a single institution, and a corresponding prospective study is needed to verify this conclusion.

Myeloid sarcoma (MS) is a rare extramedullary tumor mass that carries a high risk of progression to acute myeloid leukemia (AML), and patients with MS are commonly treated with the AML regimen. However, MS is frequently misdiagnosed due to its lack of clinical specificity. Patients with MS who harbor tumor protein p53 (TP53) mutations and complex karyotypes are considered to have a poorer prognosis. The present study reports a case of lymph node MS with TP53 (V173G)-related myelodysplastic syndrome (MDS). The mass was first considered to be a lymphoma and treated as such. However, following immunohistochemical analysis, which revealed cells positive for CD43, myeloperoxidase and CD117, the patient was later diagnosed with MS combined with MDS. The patient went into complete remission after the first cycle of chemotherapy, and showed a decrease in platelet, red blood cell and white blood cell counts following the second cycle of chemotherapy. After the third chemotherapy, agranulocytosis occurred, leading to refractory pneumonia and eventually death due to respiratory failure. MS with TP53-related MDS has a low incidence rate, a poor prognosis and a short survival time. The clinical manifestations of MS are non-specific and easy to misdiagnose, leading to delayed diagnosis and treatment, and ultimately worsening the prognosis of the patients. Therefore, a lymph node biopsy should be performed as soon as possible for patients with lymph node enlargement, and early treatment should be carried out to prolong the survival period.

Osteolytic lesions are infrequently observed in adult patients with acute myeloid leukemia (AML). This report details the case of a 66-year-old male patient who presented with myeloid sarcoma (MS), osteolytic lesion and pancytopenia. Effective treatments were delayed due to diagnostic challenges and the rapid progression of the disease. It is essential to consider AML in the differential diagnosis when faced with a patient presenting osteolytic lesions and pancytopenia.