Infant leukemia suggestive of natural killer cell precursor origin followed an unusual clinical course

Acute leukemia of dendritic cell lineage in childhood: incidence, biological characteristics and outcome

CD4+ CD56+ malignancies have only recently been related to dendritic cell (DC) lineage. The few cases described, mostly adults and elderly, typically present with cutaneous lesions, followed by disseminated tumor localizations within a few months, with a generally very aggressive course and fatal outcome, despite the different therapeutic approaches employing chemotherapy and/or radiotherapy. Considering that leukemias in childhood and in adults are different diseases, we describe three pediatric cases to help compare the biological characteristics, immunophenotype, clinical features, treatment response and incidence of this disease in both age groups. From a total 1363 new patients with acute leukemia (AL), we report three cases with blasts of French - American - British L2 morphology, an absence of the most specific markers for myeloid, T or B lineage and lacking CD34, which led us to evaluate the blasts with an extensive panel of antibodies, including those related to the other putative pathways of lymphoid differentation: natural killer and DC. The cells expressed CD4, CD56, HLA-DR, BDCA-2 and BDCA-4. None of our cases presented with skin involvement. All three children showed good response to acute lymphoblastic leukemia (ALL) protocols, achieving complete remission even when one of the patients relapsed and received an allogeneic transplant. These findings, in spite of the small number of patients, suggest that the clinical course in children might be less aggressive, and that regular ALL protocols would be effective. We emphasize the importance of including antibodies for DC lineage in cases of CD34(-) unclassifiable AL to further characterize these rare cases (0.22%), considering that the tumor cell affiliation to DC lineage relies exclusively on immunophenotypic criteria.

CD4+/CD56+ hematodermic neoplasm: blastic NK cell lymphoma in a 6-year-old child: report of a case and review of literature

A 6-year-old girl presented with disseminated polymorphous skin lesions of several months' duration, joint pains, recurrent fever, anemia, and inguinal adenopathy. Subsequent evaluation of skin, lymph node, and bone marrow morphology showed infiltration of atypical lymphocytic cells. Immunohistochemical and flow cytometric analysis showed findings consistent with the rare but highly malignant blastic Natural killer cell lymphoma/leukemia also termed CD4/CD56 hematodermic neoplasm.

CD4(+) CD56(+) Lineage-Negative Malignancies Are Rare Tumors of Plasmacytoid Dendritic Cells

CD4(+) CD56(+) lineage-negative malignancies are difficult to diagnose and classify. Recent studies have suggested that these malignancies may derive from plasmacytoid dendritic cells (pDC). In this report, we examine 10 cases of CD4+, CD56+ lineage-negative malignancies that presented in various tissue sites. The goal was to identify the morphologic, immunophenotypic, and genotypic findings to devise a diagnostic approach to tissue biopsies of these lesions and to confirm the proposed cell of origin. The mean age was 66 years (range, 45-80 years) with a male predominance (8 males/2 females). Frequent sites of disease included skin (60%) and peripheral blood/bone marrow (70%). Tumor cells were positive for CD45, CD43, CD4, and CD56 (9 of 10). The pDC markers, CD123 (9 of 10) and CD45RA (10 of 10), were detected by immunoperoxidase staining. Also noted was CD2 positivity (1 case), weak CD7 positivity (4 of 8 cases), weak CD33 (4 of 9 cases), TdT (2 cases), and CD68 (2 cases). All cases were otherwise negative for EBV (EBER), B-cell, T-cell, myeloid, and NK cell markers. T-cell receptor-gamma gene rearrangement was negative in all cases. Complex structural chromosomal abnormalities were seen in 3 of 5 cases, a subset of which may be recurrent in pDC malignancy. Overall prognosis was poor despite multiagent chemotherapy and/or radiation. Our study confirms that CD4+/CD56+ lineage-negative tumors are derived from pDC and have characteristic clinical, histopathologic, and immunophenotypic features. Furthermore, these rare neoplasms can be readily diagnosed using recently developed immunoperoxidase techniques.

Blastic natural killer cell lymphoma/leukemia (CD56-positive blastic tumor)

BACKGROUND

Blastic natural killer (NK) cell lymphoma/leukemia (BNKL) is an immature CD56-positive neoplasm, which was recognized recently and characterized by systemic proliferation of tumor cells including skin, lymph node, and bone marrow.

METHODS

The current study analyzed 47 patients with BNKL (27 had leukemias and 20 had lymphomas). Patient data were collected for the survey of the NK-Cell Tumor Study Group.

RESULTS

There were 33 males and 14 females, with a median age of 53 years (range, 3 months to 89 years). There were few clinicopathologic differences between the leukemia and lymphoma types. Cutaneous involvement was noted at diagnosis in 28 patients, who presented a tendency for older age of onset (median: 56 vs. 46 years, P = 0.11) than patients with noncutaneous BNKL. Cutaneous BNKL showed less frequent mediastinal involvement (4% vs. 53%, P = 0.0002) and less severe thrombocytopenia (P =0 .03). Phenotypic characteristics were also different, with cutaneous BNKL favoring CD4 and HLA-DR expression, and noncutaneous BNKL favoring CD16 and CD34 expression. Both groups responded well to chemotherapy for lymphoid malignancies, but disease recurrence was frequent. The prognosis of patients with noncutaneous BNKL was significantly poorer than that of patients with cutaneous BNKL (median survival: 15 vs. 25 months, P = 0.02). Multivariate analysis confirmed that cutaneous involvement was a significant and independent prognostic factor for BNKL, as were age of onset and leukocyte count.

CONCLUSIONS

These findings suggested that BNKL is a heterogeneous disease and contains at least two subtypes. Although further investigations are needed to settle a marker for distinction, the presence of cutaneous involvement is a useful prognostic factor.

Early plasmacytoid dendritic cell leukemia/lymphoma coexpressing myeloid antigenes

Early plasmacytoid dendritic cell (pDC) leukemia/lymphoma has recently been described as a CD4(+)CD56(+) lineage negative malignancy with characteristic clinical, morphologic, immunophenotypic, and biological features. We present a case of a 72-year-old man who was diagnosed with isolated skin involvement 30 months ago and received numerous chemotherapy cycles that did not prevent three relapses of the disease, the last two involving the bone marrow. The bone marrow was nearly completely infiltrated with small- to medium-sized blasts displaying a high nuclear to cytoplasmic ratio, a cytoplasm with faint basophilia lacking granulations or Auer rods. Small vacuoles surrounding the nucleus were frequently observed. Flow cytometry showed CD4(+), CD56(+), CD45(+), CD38(+), HLA-DR(+), CD33(+), CD123(+), CD2(-), cyCD3(-), CD7(-), CD10(-), CD11b(-), CD13(-), CD14(-), CD16(-), CD19(-), cyCD22(-), CD24(-), CD34(-), CD57(-), CD61(-), CD64(-), CD65(-), cyCD79a(-), CD117(-), MPO(-), and TdT(-) population. At the second bone marrow relapse, CD117 was also positive. Our patient was initially treated with acute myeloid leukemia-type chemotherapy, later he was given acute lymphoblastic leukemia-type treatment, and at the last relapse he received CHOP chemotherapy. Each treatment led to rapid response of tumor manifestations with disease-free intervals of 7 months, 9 months, and 8 months, respectively. Although patients usually have an ominous prognosis, with only 25% living more than 24 months, our patient is alive after 30+ months and has again achieved complete remission after the last chemotherapy.

Acute leukemia with natural killer cells antigens in Brazilian children

Malignancies arising from Natural Killer cells (NK) were described mainly comprising disorders related to large granular lymphocyte expansion. Clinical, morphological and immunophenotypic characteristics of myeloid/NK cell precursor acute leukemia (M/NK-AL) have been mainly described in adult patients. We identified nine children with M/NK-AL precursor cells in a series of 264 childhood acute leukemia diagnosed in our laboratory from consecutive referrals before treatment. CD34 +/-, CD13/33 +, CD11b +, a-MPO + and CD56 +, characterized these cases with TcR alphabeta and gammadelta negative cells. The differential diagnosis between subtypes of NK leukemia with those of lymphoid or myeloid origin in childhood raises the question regarding the pathogenesis and therapeutic implications of this rare entity in children.

'Agranular CD4+ CD56+ hematodermic neoplasm' (blastic NK-cell lymphoma) originates from a population of CD56+ precursor cells related to plasmacytoid monocytes

In 1999, we reported seven cases of an unusual hematologic malignancy with primary cutaneous presentation that appeared as a distinct clinicopathologic entity characterized by medium-sized tumor cells with a peculiar CD3- CD4+ CD56+ CD43+ HLA-DR+ cell surface phenotype. Because the origin of tumor cells was not clear and they exhibited a nonlineage-specific phenotype, we hypothesized that such tumors likely originated from hematologic-myeloid precursor cells and were tentatively assigned the designation "agranular CD4+ CD56+ hematodermic neoplasms." In the present study we report 14 cases (seven already reported and seven additional cases) of these tumors, and simultaneously we present now a rare population of cells that we have identified in the peripheral blood of healthy volunteers treated with Flt3 ligand. These cells express all the characteristic markers of CD4+ CD56+ hematodermic neoplasms. This population appears to be related to plasmacytoid monocytes because they also expressed CD68 and bright levels of CD123. To confirm the relationship between these normal cells and CD4+ CD56+ hematodermic neoplasms, we conducted an extensive comparative phenotypic study. Results show that these two cell types are indeed related because they share many phenotypic features, including the presence of CD4, CD56, CD43, CD68, and HLA-DR and the absence of other T, B, NK, or myelomonocytic markers. More importantly, we found that the bright expression of CD123 by immunohistochemistry is a distinctive characteristic of CD4+ CD56+ hematodermic neoplasms because all (n = 14) cases expressed this marker, whereas only two specimens in a control panel comprising 30 samples of related tumors expressed comparable levels of CD123. We therefore propose that oncogenic transformation of NCAM-expressing plasmacytoid monocyte-like cells may lead to "agranular CD4+ CD56+ hematodermic neoplasm."