Chronic myelomonocytic leukemia derived from a possible common progenitor of monocytes and natural killer cells

Plasmacytoid dendritic cell leukaemia/lymphoma: towards a well defined entity?

CD4(+)/CD56(+) haematodermic neoplasm or 'early' plasmacytoid dendritic cell leukaemia/lymphoma (pDCL) was described as a disease entity in the last World Health Organisation/European Organisation for Research and Treatment of Cancer classification for cutaneous lymphomas. These leukaemia/lymphomas co-express CD4 and CD56 without any other lineage-specific markers and have been identified as arising from plasmacytoid dendritic cells. Despite a fairly homogeneous pattern of markers expressed by most pDCL, numerous distinctive features (e.g. cytological aspects and aberrant marker expression) have been reported. This may be related to the 'lineage-independent developmental' programme of dendritic cells, which may be able to develop from either immature or already committed haematopoietic progenitors. This highlights the need for specific validated markers to diagnose such aggressive leukaemia. Here, we propose--among others (e.g. T-cell leukaemia 1)--blood dendritic cell antigen-2 and high levels of CD123 expression as potential markers. In addition, we propose a multidisciplinary approach including several fields of haematology to improve pDCL diagnosis.

TNFα stimulates NKG2D-mediated lytic activity of acute myeloid leukemic cells

The mechanism by which leukemic cells interfere with normal hematopoiesis remains unclear. We show here that, whereas the leukemic KG1a cells are naturally devoid from cellular cytotoxicity, once activated by TNFalpha, they display cytolytic activity toward various cellular targets including CFU-GM. This mechanism is dependent on stimulation of the granzyme B/perforin system. In addition, KG1a cells expressed the NKG2D receptor and its signal-transducing adaptator DAP 10, which were functional as confirmed by redirected lysis experiments. Interestingly, flow cytometry analysis of 20 samples of patients with acute myeloid leukemia (AML) (FAB M0-M5) revealed the expression of NKG2D (40%) and other natural cytotoxicity receptors (40% for NKp30, 74% for NKp44, 39% for NKp46) by a pool >15% of leukemic cells. Furthermore, CD34+ hematopoietic progenitors undergoing granulomonocytic differentiation expressed NKG2D ligands. Altogether, we propose a model in which, upon stimulation by TNFalpha, leukemic cells may exert cytotoxicity against myeloid progenitors. This finding may have important clinical implications in the context of diseases characterized by TNFalpha accumulation, such as AML or myelodisplasic syndromes.

Blastic natural killer-cell lymphoma of the skin associated with myelodysplastic syndrome or myelogenous leukaemia: a coincidence or more?

We report three patients with blastic natural killer (NK)-cell lymphoma of the skin associated with myelodysplastic syndrome (MDS) (two patients) or subacute myelomonocytic leukaemia (one patient). In two patients MDS was diagnosed before skin lesions; the patient with leukaemia initially presented with skin lesions. Our patients had several clinical features in common, namely multiple skin lesions with a bruise-like appearance, involvement of the oral mucosa, and good general status at presentation but very rapid deterioration in the course of the disease. All patients died of disease 4-14 months after the diagnosis. Histopathologically, there were cutaneous infiltrates of slightly pleomorphic medium-sized cells expressing CD4, CD56, terminal deoxynucleotidyl transferase (focally) and being negative for surface CD3, cytotoxic molecules, B-cell-associated markers and myelomonocytic markers. Erythrocyte extravasation was seen in all patients. T-cell receptor genes were in germline configuration. MDS was classified as refractory cytopenia with multilineage dysplasia and ring sideroblasts and refractory anaemia with transition to refractory anaemia with excess of blasts. We reviewed similar cases reported in the literature showing coexistence of blastic NK-cell lymphoma/leukaemia and MDS or myelogenous leukaemia. We conclude that given an overall limited number of reported cases of blastic NK-cell lymphoma/leukaemia, its association with various myelodysplastic/myeloproliferative disorders seen in a subset of patients ( approximately 15-20%) is more than coincidental and may indicate their common origin.

Expression of NK-associated antigens in extramedullary lymph nodal blast crisis of chronic myeloid leukemia on fine-needle cytology

A case is reported of a 62-yr-old male suffering from chronic myelogenous leukemia (CML) who developed an extramedullary, para-orthic lymph-nodal blast crisis without blood or bone marrow involvement and expression of CD56/NK associated marker. The diagnosis was performed on ultrasound-guided fine-needle cytology by an immunocytochemical and flow cytometric analysis. Conventional smears showed a monomorphous population of disperse, undifferentiated cells without cytoplasm. Cells showed fragile nuclei, vesicular chromatin, and evident nucleoli. Immunocytochemistry performed on cytospin slides were negative for cytokeratin, LCA, CD20, CD45Ro, and myeloperoxidase (MPO). Flow cytometry analysis proved the myeloid origin of the tumor by expression of CD13, CD34, and CD38 and showed aberrant expression of CD56. Cytological diagnosis was confirmed by histological examination. CD56 expression is generally an expression of NK lymphoid proliferation and may be observed in acute myelogenous leukemia but has rarely been reported in CML and its related blast crisis. This unusual expression, its possible explanation, the related technical problems, and clinicopathological aspects are discussed.

CD56(+) TdT(+) blastic natural killer cell tumor of the skin: a primitive systemic malignancy related to myelomonocytic leukemia

BACKGROUND

An unusual cutaneous tumor that has blastic morphology and coexpresses CD56 and terminal deoxynucleotidyl transferase (TdT) has been recently recognized and termed blastic natural killer cell lymphoma.

METHODS

The authors identified seven cases of such CD56(+)TdT(+) blastic tumors presenting in skin at their institution. The authors correlated clinical course with histomorphology and immunophenotype.

RESULTS

All 7 patients (6 men, 1 woman, 52-85 years) presented with rapidly growing, frequently multiple cutaneous nodules. All patients had low level bone marrow involvement at diagnosis and frequently had lymph node involvement. Tumor cells were of intermediate size with irregular nuclear contours, fine chromatin, and indistinct small nucleoli. The expression of TdT varied between 5% and over 90% of the neoplastic cell population. Tumor cells were negative for surface CD3, CD5, and CD20 in all cases, but some patients showed expression of CD2 (three out of five), cytoplasmic CD3 (two out of seven), CD4 (six out of seven), and CD16 (three out of seven). Molecular studies showed absence of T-cell receptor gene rearrangements in all cases. All seven patients had rapid progression of disease, and six patients have died of their disease or complications. Three patients developed progressively increasing numbers of bone marrow blasts that had a myeloid immunophenotype and were negative for TdT and CD56. Two patients met criteria for acute myeloid leukemia at 11 and 22 months after presentation, respectively.

CONCLUSIONS

CD56(+) TdT(+) blastic tumor presenting in skin is a systemic malignancy likely of primitive/undifferentiated hematopoietic origin. Patients might subsequently develop tumors of myeloid or myelomonocytic phenotype, indistinguishable from acute myelogenous leukemia.