CD2-, CD4+, CD56+ agranular natural killer cell lymphoma of the skin

Human BDCA2+CD123+CD56+ dendritic cells (DCs) related to blastic plasmacytoid dendritic cell neoplasm represent a unique myeloid DC subset

Dendritic cells (DCs) comprise two functionally distinct subsets: plasmacytoid DCs (pDCs) and myeloid DCs (mDCs). pDCs are specialized in rapid and massive secretion of type I interferon (IFN-I) in response to nucleic acids through Toll like receptor (TLR)-7 or TLR-9. In this report, we characterized a CD56⁺ DC population that express typical pDC markers including CD123 and BDCA2 but produce much less IFN-I comparing with pDCs. In addition, CD56⁺ DCs cluster together with mDCs but not pDCs by genome-wide transcriptional profiling. Accordingly, CD56⁺ DCs functionally resemble mDCs by producing IL-12 upon TLR4 stimulation and priming naïve T cells without prior activation. These data suggest that the CD56⁺ DCs represent a novel mDC subset mixed with some pDC features. A CD4⁺CD56⁺ hematological malignancy was classified as blastic plasmacytoid dendritic cell neoplasm (BPDCN) due to its expression of characteristic molecules of pDCs. However, we demonstrated that BPDCN is closer to CD56⁺ DCs than pDCs by global gene-expression profiling. Thus, we propose that the CD4⁺CD56⁺ neoplasm may be a tumor counterpart of CD56⁺ mDCs but not pDCs.

Plasmacytoid dendritic cell leukemia in children

CD4/CD56 malignancies are rare hematologic neoplasms, which have recently been shown to represent the malignant counterpart of plasmacytoid dendritic cells (pDC). A 5-year-old boy initially presented with multiple subcutaneous lesions on his upper and lower extremities. Skin biopsy results showed large atypical lymphoid cells in the dermis. The blast cells were stained with CD4 and CD56. In the bone marrow aspirate, 20% of the blast cells were found. The patient was diagnosed as acute unclassified leukemia and received chemotherapy designed for the treatment of acute myeloid leukemia. He achieved a complete remission that lasted for 8 months. However, multiple subcutaneous lesions recurred 1 month after the end of the therapy, with increasing blast cells in his blood. Immunophenotypically, the blast cells were positive for CD2, CD4, CD7, and CD56, and negative for CD3, CD13, CD19, CD33, and CD34 antigens. The blast cells were positive for CD123 (interleukin-3 receptor alpha chain) and blood dendritic cell antigen-2, which are expressed on pDC. The patient was diagnosed as acute leukemia derived from pDC. The CD4, CD56, CD3, CD13, CD19, CD33 profile is highly suggestive of this disease, and the CD123 and blood dendritic cell antigen-2 markers are useful in helping to diagnose pDC leukemia.

Novel markers of normal and neoplastic human plasmacytoid dendritic cells

Plasmacytoid dendritic cells (pDCs) are involved in innate immunity (eg, by secreting interferons) and also give rise to CD4+CD56+ hematodermic neoplasms. We report extensive characterization of human pDCs in routine tissue samples, documenting the expression of 19 immunohistologic markers, including signaling molecules (eg, BLNK), transcription factors (eg, ICSBP/IRF8 and PU.1), and Toll-like receptors (TLR7, TLR9). Many of these molecules are expressed in other cell types (principally B cells), but the adaptor protein CD2AP was essentially restricted to pDCs, and is therefore a novel immunohistologic marker for use in tissue biopsies. We found little evidence for activation-associated morphologic or phenotypic changes in conditions where pDCs are greatly increased (eg, Kikuchi disease). Most of the molecules were retained in the majority of pDC neoplasms, and 3 (BCL11A, CD2AP, and ICSBP/IRF8) were also commonly negative in leukemia cutis (acute myeloid leukemia in the skin), a tumor that may mimic pDC neoplasia. In summary, we have documented a range of molecules (notably those associated with B cells) expressed by pDCs in tissues and peripheral blood (where pDCs were detectable in cytospins at a frequency of <1% of mononuclear cells) and also defined potential new markers (in particular CD2AP) for the diagnosis of pDC tumors.

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.

CD56+ hematological neoplasms presenting in the skin: a retrospective analysis of 23 new cases and 130 cases from the literature

BACKGROUND

The aim of this study was to define prognostic parameters and guidelines for diagnosis and treatment for CD56+ hematological neoplasms with first presentation in the skin.

PATIENTS AND METHODS

The study group included 153 cases (23 new and 130 from the literature). According to the World Health Organization classification, the group included 15 nasal and 38 nasal-type natural killer (NK)/T-cell lymphomas, 63 blastic NK-cell lymphomas, 14 cutaneous CD30+ lymphoproliferations, 10 cases of myeloid leukemia, six cases of subcutaneous panniculitis-like T-cell lymphoma (SCPLTCL) and seven peripheral T-cell lymphomas, unspecified.

RESULTS

In general, these CD56+ hematological neoplasms had a poor prognosis, with only 27% of patients alive after a median follow-up of 12 months. The median survival was 13 months. Nasal and nasal-type NK/T-cell lymphomas and CD56+ SCPLTCL had the worst prognosis, with a median survival of 5, 6 and 5 months, respectively. Only nasal-type NK/T-cell lymphomas presenting with only skin lesions had a somewhat better prognosis (median survival 27 months). In blastic NK-cell lymphomas (median survival 14 months), age </=40 years, aggressive treatment with acute leukemia protocols and high TdT expression were associated with a more favorable prognosis. Striking similarities in histology, immunophenotype, clinical presentation and clinical behavior were found between blastic NK-cell lymphomas and CD56+ myeloid leukemias.

CONCLUSIONS

CD56+ hematological neoplasms presenting in the skin have a poor prognosis, except for primary cutaneous CD30+ lymphoproliferations. The striking similarities between blastic NK-cell lymphomas and CD56+ myeloid leukemias presenting in the skin provide a rationale to treat these patients with more aggressive regimens, rather than with CHOP(-like) regimens and radiotherapy, which have proven to be inadequate therapies for this neoplasm.

Plasmacytoid dendritic cells: from the plasmacytoid T-cell to type 2 dendritic cells CD4+CD56+ malignancies

Recent identification of CD4(+)CD56(+) malignancies as pathological counterparts of the precursors of type 2 dendritic cells (DC2) has shed new light on a leukocyte lineage that long remained elusive. This review retraces how knowledge evolved, through careful examination and analysis of both normal lymphoid tissue and rare proliferative diseases, from plasmacytoid T cells to plasmacytoid dendritic cells (pDC) and then DC2. The functions of these cells and their key role at the crossroads of innate and cognitive immunity are also discussed. The major characteristics of DC2 malignancies are summarized and compared to natural killer cell (NK) lymphomas, another type of proliferative disease sharing the expression of CD56.

What is CD4+CD56+ malignancy and how should it be treated?

CD4+CD56+ malignancy is a rare neoplasm with a typical clinical pattern, an aggressive course and high early relapse rate despite good initial response to chemotherapy. In this review, the impact of different therapeutic approaches on clinical outcome has been studied. We evaluated 91 published cases and our own six patients in terms of clinical features, immunophenotype/cytogenetics and treatment outcome. Treatment was divided into four groups: (A) chemotherapy less intensive than CHOP; (B) CHOP and CHOP-like regimens; (C) therapy for acute leukemia; (D) allogeneic/autologous stem cell transplantation. The median overall survival was only 13 months for all patients. Patients with skin-restricted disease showed no difference in the overall survival from patients with advanced disease (17 and 12 months, respectively). Age >/=60 years was a negative prognostic factor. Age-adjusted analysis revealed improved survival after high-dose chemo/radiotherapy followed by allogeneic stem cell transplantation when performed in first complete remission. This therapeutic approach should be recommended for eligible patients with CD4+CD56+ malignancy. For older patients the best treatment option is still unknown.

'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."

Pediatric acute blastic natural killer cell leukemia

The goal of this report is to describe a rare case of pediatric blastic natural killer (NK) cell leukemia and to compare pediatric blastic NK cell leukemia/lymphoma to other reported cases of pediatric NK cell leukemia. The patient, a 9-year-old girl, presented with acute leukemia with a phenotype similar to adult blastic NK cell leukemia/lymphoma. The blasts were agranular and expressed CD7, 45, 56, and HLA-DR, but not CD3, 11c, 13, 33, or TdT. She had a complete response to ALL-directed chemotherapy, but had multiple relapses involving the cerebrospinal fluid, nasal sinus, lymph node and skin. In addition to the reported case, a review of the literature identified 9 previously reported cases of NK cell leukemia in patients 18 years of age or less. Cases were subdivided into blastic, acute/aggressive, and myeloid precursor NK cell leukemia based upon CD13/33 expression and morphologic characteristics. Compared to pediatric acute/aggressive NK cell leukemia, children with blastic NK cell leukemia showed greater variation in age and race. Prognosis was poor for all groups. Pediatric blastic NK cell leukemia is a distinct clinicopathologic entity which differs from other types of pediatric NK cell leukemia.

A case of primary cutaneous CD56+, TdT+, CD4+, blastic NK-cell lymphoma in a 19-year-old woman

The classification of blastic or blastoid natural killer (NK)-cell lymphoma is controversial. Reports of primary cutaneous blastic CD56+ NK-cell lymphoma are rare, which necessitates further clinicopathologic definition of this type of lymphoma. Most CD56+ lymphomas display angiocentric histologic features, especially in Asian patients, and these are mostly associated with the presence of Epstein-Barr virus (EBV) genome and with an aggressive clinical course. We report on a young woman with a primary cutaneous blastic NK lymphoma which showed no angiocentric features but showed an unusual immunophenotype; CD56+, TdT+, CD4+, EBV-, and germline configuration of T-cell receptor gene. This unusual lymphoblastic lymphoma seems to have an immature or progenitor NK cell lineage.

Blastic natural killer cell lymphoma/leukemia: a report of seven cases

Only a few blastic natural killer (NK) cell leukemias and lymphomas have been reported. As such, the clinicopathologic spectrum of this disease is incompletely understood. We report 7 cases of blastic NK cell lymphoma/leukemia. All patients were men, 5 white and 2 Arab American. All cases exhibited blastic morphologic features and were CD3- and CD56+ with germline T-cell receptor genes. Five cases were CD4+ and involved the skin. Both CD4- cases never involved the skin. Other markers of mature NK cells such as CD16, CD57, and TIA-1 were expressed infrequently. Three cases were CD33+. One CD33+ case had a clonal rearrangement of the immunoglobulin heavy chain gene. Skin and lymph nodes were involved most often, with frequent evolution to a leukemic phase. Initial responses to therapy were achieved in most patients, but the tumors invariably recurred.

CD2- CD4+ CD56+ hematodermic/hematolymphoid malignancy

BACKGROUND

CD2- CD4+ CD56+ lymphoid malignancy has been only rarely reported the last 5 years. It is characterized by a high incidence of cutaneous involvement, cytologically agranular cells, aggressive clinical course, and negative Epstein-Barr virus (EBV) involvement.

OBSERVATION

We describe a Japanese patient with a unique hematolymphoid malignancy characterized by an involvement of skin, nasopharyngeal region, bone marrow, lymph node, and a CD4+ CD43+ CD56+ CD2- CD3- CD8- and terminal deoxynucleotidyl transferase phenotype. Clinically, the cutaneous eruptions were purplish, hard, multiple nodules. Histologically, a massive proliferation of atypical pleomorphic cells with medium-sized nuclei were observed throughout the dermis. No clonal rearrangement of T-cell receptor (TCR)-beta gene or immunoglobulin heavy chain J gene was found, and no positive identification of EBV by in situ hybridization for EBV-encoded small nuclear RNA was found. The patient underwent high-dose chemotherapy with autografting of peripheral blood stem cells; however, the tumors quickly relapsed.

CONCLUSION

We gathered data from 17 cases of lymphoid malignancy from the literature sharing immunophenotypic and genotypic features similar to those of our case, including CD2- CD4+ CD56+ and germline rearrangement of TCR. Although the cellular origin could not be decided, this malignancy was found to have 100% affinity for skin, a short course, and poor prognosis.

Solitary primary cutaneous CD30+ large cell lymphoma of natural killer cell phenotype bearing the t(2;5)(p23;q35) translocation and presenting in a child

Primary cutaneous CD30+ large cell lymphoma is an unusual tumor most commonly seen in adults. Most of these lymphomas are of T-cell origin and carry a good prognosis. We present the case of a 4-year-old girl with stage IEA CD30+ large cell lymphoma with a CD56+ natural killer cell phenotype and the t(2;5)(p23;q35) translocation. After excision, the patient has been free of disease for 44 months. Primary cutaneous CD30+ large cell lymphoma is uncommon in children. To our knowledge, primary cutaneous CD30+ natural killer type lymphoma has not been reported previously. The indolent behavior of this tumor indicates its similarity to other primary cutaneous CD30+ large cell lymphomas and its difference from other CD56+ lymphomas involving the skin, which often exhibit an aggressive clinical course. Cases such as this one illustrate why the use of a single, or even a few, immunohistochemical stains can be misleading in regard to lymphoma classification and prognostication.

Primary cutaneous lymphomas

Primary cutaneous lymphomas have a distinct clinical behavior and prognosis, and therefore require a different therapeutic approach, as compared with their primary nodal equivalents. The European Organization for Research and Treatment of Cancer (EORTC) classification for primary cutaneous lymphomas recognizes a limited number of cutaneous T-cell lymphomas and cutaneous B-cell lymphomas and is at present the best guide to optimal management and treatment of these conditions. Herein, the relationship between the EORTC classification and the recently published World Health Organization classification is discussed, and recent developments regarding the main types of cutaneous T-cell lymphomas and cutaneous B-cell lymphomas recognized in the EORTC classification are presented.