Acute monocytic leukemia diagnosed by flow cytometry includes acute myeloid leukemias with weakly or faintly positive non-specific esterase staining.

A diagnosis of acute monocytic leukemia (AML-M5) based on α-naphthyl butyrate esterase (α-NB) staining has some problems, because AML-M5 leukemic cells often show weak or faint positivity on α-NB staining. In these situations, some cases of AML-M5 tend to be misdiagnosed as AML-M0. Therefore, we evaluated the significance of weak or faint α-NB staining in AML-M5 diagnosed by flow cytometry (FCM). Nineteen AML cases in which leukemic cells were negative for naphthol AS-D chloroacetate esterase staining were studied. For FCM, we defined leukemic cells as having a monocytic nature when more than 10% of the leukemic cells were positive for at least one of the following antigens: CD4, CD11c, CD14, and CD64. The monocytic nature determined by FCM was consistent with positive or weak positivity on α-NB staining. Five of 6 cases in which leukemic cells exhibited faint positivity for α-NB staining could be diagnosed as AML-M5 by FCM, while negative α-NB staining was consistent with a diagnosis of AML-M0. These results suggest that AML-M5 should be taken into consideration even when leukemic cells are faintly positive for α-NB staining.

Acquired TET2 mutation in one patient with familial platelet disorder with predisposition to AML led to the development of pre-leukaemic clone resulting in T2-ALL and AML-M0.

Familial platelet disorder with predisposition to acute myeloid leukaemia (FPD/AML) is characterized by germline RUNX1 mutations, thrombocytopaenia, platelet dysfunction and a risk of developing acute myeloid and in rare cases lymphoid T leukaemia. Here, we focus on a case of a man with a familial history of RUNX1R174Q mutation who developed at the age of 42 years a T2-ALL and, 2 years after remission, an AML-M0. Both AML-M0 and T2-ALL blast populations demonstrated a loss of 1p36.32-23 and 17q11.2 regions as well as other small deletions, clonal rearrangements of both TCRγ and TCRδ and a presence of 18 variants at a frequency of more than 40%. Additional variants were identified only in T2-ALL or in AML-M0 evoking the existence of a common original clone, which gave rise to subclonal populations. Next generation sequencing (NGS) performed on peripheral blood-derived CD34+ cells 5 years prior to T2-ALL development revealed only the missense TET2P1962T mutation at a frequency of 1%, which increases to more than 40% in fully transformed leukaemic T2-ALL and AML-M0 clones. This result suggests that TET2P1962T mutation in association with germline RUNX1R174Q mutation leads to amplification of a haematopoietic clone susceptible to acquire other transforming alterations.

Granulocytic Sarcoma in an Adult with Relapsed Acute Myeloid Leukaemia.

Granulocytic sarcoma is an extramedullary tumour consisting of malignant granulocytic precursor cells that is common among children with acute myeloid leukaemia (AML). We report a case of orbital granulocytic sarcoma in an adult with relapsed undifferentiated AML-M0. It presented as bilateral medial canthal swellings. An incisional biopsy confirmed the diagnosis of granulocytic sarcoma. The swelling resolved with re-induction chemotherapy.

A Case of Minimally Differentiated Acute Leukemia (AML-M0) Complicated by Ventricle Thrombosis During Remission-induction.

Sudden chest pain, dyspnea, and tachypnea occurred in a 21-year-old female who was undergoing induction chemotherapy under a diagnosis of minimally differentiated acute leukemia (M0). The arterial blood gas (ABG) tensions were decreased (PO2 71.6 mm Hg, PCO2 23.7 mm Hg), and an electrocardiogram showed a right-bundle branch block. Coagulation abnormalities (PT 73.1%, APTT 39.4 s, FDP 235mg/dl) were observed 72 h before onset. Echocardiography revealed a large thrombus in a right ventricle. A diagnosis of pulmonary thromboembolism (PTE) was made, and a tissue-type plasminogen activator (monteplase) was administered under percutaneous cardiopulmonary support (PCPS). The complete lysis of thrombus was confirmed by an echocardiogram 8 h later. Symptoms and ABG data were also improved. PTE in adult AML cases is rare, but should be considered as one of the life-threatening complications in AML patients under chemotherapy who develop respiratory difficulties. We suggest a careful monitoring of coagulation abnormalities for the prediction of PTE during chemotherapy for AML, and the use of tissue-type plasminogen activator (t-PA), monteplase, for the treatment of PTE in these cases.