A CD56-negative case of blastic natural killer-cell lymphoma (agranular CD4+/CD56+ haematodermic neoplasm)

Flow Cytometry Identifies a Spectrum of Maturation in Myeloid Neoplasms Having Plasmacytoid Dendritic Cell Differentiation

BACKGROUND

Neoplasms derived from plasmacytoid dendritic cells (PDCs) are currently divided into two broad categories: mature PDC proliferations associated with myeloid neoplasms (MPDMN) and blastic plasmacytoid dendritic cell neoplasm (BPDCN); only BPDCN is recognized in the WHO 2016 classification of hematopoietic neoplasms. We present seven patients with high grade myeloid neoplasms (MNs), mostly acute leukemias, having a spectrum of PDC differentiation and not fitting with MPDMN or BPDCN.

METHODS

We analyzed seven MN cases having increased myeloblasts and prominent CD56-negative PDC proliferations comprising 5-26% of bone marrow or blood cellularity as measured by flow cytometry. The cases included five acute myeloid leukemia (three FAB M4 subtype, two unclassified), one mixed phenotype acute leukemia, and one case of unclassified MN.

RESULTS

Six cases demonstrated immunophenotypic evidence of PDC differentiation from leukemic blasts, based on variable expression of CD34, CD45, CD123, and CD304 by the leukemic cells. Four cases had circulating PDC populations in blood. None of the cases met clinical or pathologic criteria for BPDCN. Morphologic review was available for four acute leukemia cases and demonstrated either nodular or interstitial infiltrates of PDCs. All cases had an aggressive clinical course, and three cases had FLT3 ITD mutation.

CONCLUSIONS

These cases demonstrate that high grade MNs, in particular AML, can exhibit PDC differentiation, with or without monocytic differentiation, in a manner distinct from MPDMN or BPDCN. The existence of MNs with immature PDC proliferations suggests that there is a broader spectrum of PDC-associated neoplasms than currently recognized. © 2019 International Clinical Cytometry Society.

Blastic Plasmacytoid Dendritic Cell Neoplasm: Analysis of Clinicopathological Feature and Treatment Outcome of Seven Cases

BACKGROUND

Blastic plasmacytoid dendritic cell neoplasm (BPDCN), which is derived from the precursor of plasmacytoid dendritic cells, is a rare and highly aggressive hematologic malignancy. It has only recently been recognized as a distinct entity. BPDCN characteristically has a predilection for cutaneous involvement.

OBJECTIVE

The aim of this study was to describe the clinical and pathological features of BPDCN, and to review the treatment courses to analyze the prognosis and the optimal therapeutic approach.

METHODS

We retrospectively reviewed seven BPDCN cases registered in the Samsung Medical Center database between January 2010 and December 2014.

RESULTS

The median age of the patients was 52 years (range, 18~79 years), and six patients were male. The clinical staging was as follows: skin (n=5), lymph node (n=6), bone marrow (n=4), and peripheral blood (n=2). The skin manifestations were bruise-like tumefaction (n=4), erythematous nodule (n=4), or multiple erythematous papules (n=1). The pathological evaluation revealed dense diffuse or nodular infiltration of neoplastic cells, which were positive for CD4, CD56, and CD123 in the immunohistochemical analysis. Six patients received multiagent chemotherapy as the first-line treatment, alone (n=4), or followed by stem cell transplantation (SCT, n=1) or concurrent radiotherapy (n=1). The median progression-free survival after the first-line treatment was 6 months (range, 2~12 months).

CONCLUSION

Three different skin manifestations were observed, with pathological features analogous to each other. All patients who received chemotherapy without SCT achieved partial or complete response but experienced relapse. Furthermore, they showed various clinical courses irrelevant to the cutaneous involvement.

Leukemic manifestation of blastic plasmacytoid dendritic cell neoplasm lacking skin lesion : a borderline case between acute monocytic leukemia

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare hematologic malignancy with a poor prognosis. We encountered a unique case of BPDCN that was leukemic at presentation without skin lesion and expressed CD33 antigen. A 74-year-old man was admitted because of dyspnea. Physically, hepatosplenomegaly, but not skin lesions and superficial lymph node swelling, was noted. The white blood count was 33.6 × 10(9)/L with 19% giant abnormal cells. These cells were positive for CD4, CD86, CD123 (bright), BDCA-2, and HLA-DR, but negative for CD1a, CD3, CD11b, CD11c, CD13, CD14, CD19, CD64, and CD68. From these findings, a diagnosis of BPDCN was made. In terms of unusual expression, these tumor cells were positive for CD33 but negative for CD56. The karyotype was 47, XY, t(6;8) (p21;q24), + r. We performed combination chemotherapy (Ara-C + VP-16 + MIT), which resulted in a marked reduction of tumor cells and improvement of the dyspnea. On day 16, however, he died of sepsis due to Bacillus cereus. The clinical picture of this patient is unusual and may provide new information on the clinicopathology of BPDCN.

Comments on cutaneous lymphomas: since the WHO-2008 classification to present

The last classification of lymphomas of the World Health Organization in 2008 made a few changes from the preceding classification. Although useful, at the same time, it has posed new questions, concerns, and dilemmas which have been raised in the literature. The current report highlights some of these controversies, of each of these primary cutaneous entities, going through cutaneous mature T-cell and NK-cell neoplasms, mature B-cell neoplasms, precursor neoplasms, and other entities, which for several reasons do not fit in the previous categories. It also reviews some advances on many of these lymphomas published in the last 2 years.

Histologic and immunohistologic characterization of skin localization of myeloid disorders: a study of 173 cases

A retrospective analysis of 173 skin biopsy specimens of myeloid leukemia cutis (MLC) was performed to determine histologic and immunophenotypic criteria that could distinguish the varied myeloid disorders from one another. For the study, 11 relevant histologic items were scored and 12 antigens were studied (CD68 [KP1], CD163, CD14, CD4, myeloperoxidase [MPO], CD33, CD117, CD34, CD56, MIB-1, CD303, and CD123). Underlying myeloid disorders were essentially acute myeloid leukemias (65.3%), chronic myelomonocytic leukemias (11.0%), and refractory anemia (10.4%). Skin lesions were de novo in 7.5%, concurrent in 26.6%, and subsequent in 60.7%. Several morphologic characteristics (density, size of tumor cells, inflammatory background) were statistically useful in distinguishing between varied myeloid disorders. De novo MLCs displayed a specific morphologic profile. Association of CD68, CD33, and MPO could diagnose 100% of the cases of MLC. However, the immunohistochemical panel could not distinguish between the varied underlying myeloid disorders, with the exception that CD123 was particularly powerful in recognizing chronic myelomonocytic leukemia and also permitted reclassification of 4 cases as blastic plasmacytoid dendritic cell neoplasm.

Plasmacytoid dendritic cells: physiologic roles and pathologic states

Plasmacytoid dendritic cells (PDCs) have perplexed pathologists for decades, undergoing multiple adjustments in nomenclature as their lineage and functions have been characterized. Although PDCs account for less than 0.1% of peripheral blood mononuclear cells, they serve as a principal source of interferon-alpha and are also known as interferon-I producing cells (IPCs). Upon activation in vitro, they can differentiate into dendritic cells, and recent studies have substantiated a potential role in antigen presentation. Thus, PDCs may act as a link between innate and adaptive immunity. Normally found in small quantities in primary and secondary lymphoid organs, PDCs accumulate in a variety of inflammatory conditions, including Kikuchi-Fujimoto lymphadenopathy, hyaline-vascular Castleman disease, and autoimmune diseases, and in certain malignancies such as classical Hodgkin lymphoma and carcinomas. Demonstrating potential for neoplastic transformation reflective of varying stages of maturation, clonal proliferations range from PDC nodules most commonly associated with chronic myelomonocytic leukemia to the rare but highly aggressive malignancy now known as blastic plasmacytoid dendritic cell neoplasm (BPDCN). Formerly called blastic natural killer cell lymphoma or CD4/CD56 hematodermic neoplasm, BPDCN, unlike natural killer cell lymphomas, is not associated with Epstein-Barr virus infection and is generally not curable with treatment regimens for non-Hodgkin lymphomas. In fact, this entity is no longer considered to be a lymphoma and instead represents a unique precursor hematopoietic neoplasm. Acute leukemia therapy regimens may lead to sustained clinical remission of BPDCN, with bone marrow transplantation in first complete remission potentially curative in adult patients.

Extended diagnostic criteria for plasmacytoid dendritic cell leukaemia

The diagnosis of plasmacytoid dendritic cell leukaemia (pDCL) is based on the immunophenotypic profile: CD4(+) CD56(+) lineage(neg) CD45RA(+)/RO(neg) CD11c(neg) CD116(low) CD123(+) CD34(neg) CD36(+) HLA-DR(+). Several studies have reported pDCL cases that do not express this exact profile or expressing some lineage antigens that could thus be misdiagnosed. This study aimed to validate pDCL-specific markers for diagnosis by flow-cytometry or quantitative reverse transcription polymerase chain reaction on bone marrow samples. Expression of markers previously found in normal pDC was analysed in 16 pDCL, four pDCL presenting an atypical phenotype (apDCL) and 113 non-pDC - lymphoid or myeloid - acute leukaemia. CD123 was expressed at significantly higher levels in pDCL and apDCL. BDCA-2 was expressed on 12/16 pDCL and on 2/4 apDCL, but was never detected in the 113 non-pDC acute leukaemia cases. BDCA-4 expression was found on 13/16 pDCL, but also in 12% of non-pDC acute leukaemia. High levels of LILRA4 and TCL1A transcripts distinguished pDCL and apDCL from all other acute leukaemia (except B-cell acute lymphoblastic leukaemia for TCL1A). We thus propose a diagnosis strategy, scoring first the CD4(+) CD56(+/-) MPO(neg) cCD3(neg) cCD79a(neg) CD11c(neg) profile and then the CD123(high), BDCA-2 and BDCA-4 expression. Atypical pDCL can be also identified this way and non-pDC acute leukaemia excluded: this scoring strategy is useful for diagnosing pDCL and apDCL.

CD4-negative variant of CD4+/CD56+ hematodermic neoplasm: description of three cases

BACKGROUND

CD4+/CD56+ hematodermic neoplasm (HN) (blastic natural killer (NK)-cell lymphoma) is a rare entity characterized by dense, monomorphous infiltrates of medium-sized cells with blastic appearance and a characteristic immunophenotype (positivity for CD4, CD56 and CD123). The combination of CD4 and CD56 positivity is thought to be so striking that it has been used to name this entity.

METHODS

Three cases of HN with ambiguous phenotypic profile were included in this study. In all cases, phenotypic, molecular and in situ hybridization studies were carried out.

RESULTS

All three cases showed an aberrant phenotype with negativity for CD4.

CONCLUSIONS

CD4-negative or CD56-negative cases of HN have been rarely reported in the literature and represent a diagnostic problem. Our three cases confirm that CD4 is not always expressed in these neoplasms. The term 'CD4+/CD56+ hematodermic neoplasm' adopted in the World Health Organization-European Organization for Research and Treatment of Cancer classification of cutaneous lymphomas may be misleading and should probably be revised in the light of all data published in the literature.

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.

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.

Localisations cutanées révélatrices d’une hématodermie CD4+ CD56+ CD123+ : 2 cas

BACKGROUND

Agranular CD4+ CD56+ hematodermic neoplasm (blastic NK-cell lymphoma) has been recently described. The skin is often the first organ involved.

OBSERVATIONS

Two old men of respectively 70 and 77 years consulted for infiltrated cutaneous lesions. Preliminary histological examination of cutaneous biopsy taken in both patients showed a malignant proliferation suggesting a cutaneous lymphoma, and the patients were referred. Histological examination of new biopsies showed a very similar proliferation in the 2 cases of monotonous medium-sized mononuclear cells without expression of the common antigens CD3 and CD20 and the expression of CD4, CD56, and CD123. No rearrangement of the T-cell receptor gene or the immunoglobulin heavy chain gene were evidenced. No extracutaneous involvement was initially detected in the first patient. Thrombocytopenia associated with the abnormal presence of 15 p. 100 of circulating CD4+ CD56+ cells was initially found in the second patient. The first patient was treated with chemotherapy, with complete remission. A cutaneous relapse promptly occurred, followed by bone and cerebral localizations. The patient died one year after the diagnosis of the disease, in spite of intensification of the treatment. Treatment is still ongoing in the second patient.

COMMENTS

The histological presentation of these two patients was very similar with an unusual phenotype of tumor cells expressing CD4, CD56, CD123, but not expressing CD3 and CD20. Some cases have been published under the "term of blastic NK lymphoma" which is the actual term for the disease in the WHO classification. However, the tumor cells derive from the dendritic plasmacytoid cells, also called type 2 dendritic cells, and perhaps from a common precursor to lymphocyte T and dendritic plasmacytoid cells. In spite of complete cutaneous response in the 2 cases presented, as in other reports, extra-cutaneous involvement occurs quickly. Overall survival is usually poor since nearly all the patients died in less than 3 years. This justifies attempting aggressive protocols, with bone marrow allograft in the younger patients.

Les hématodermies CD4/CD56

Hematodermic CD4/CD56 neoplasm is a recently described entity. This name has been initially proposed by the French Study Group on Cutaneous Lymphomas which established the primary anatomoclinical and pathogenic and cytogenic bases of the disease in 1999. This descriptive and provisional name allowed conceptualizing the entity by its main clinical and phenotypical characteristics. The first case in the literature goes back to 1994. Since that time, several other cases have been published. The expression of CD56 led most of the authors to propose an NK-cell lineage origin. In the last WHO classification of lymphomas, the entity was indexed under the name of "blastic NK-cell lymphoma". However, the authors underlined that there were currently no clues to the etiology of blastic NK-cell lymphoma and that the precise lineage of this disease was still unresolved. At the clinical level the main characteristics of the disease are the skin tropism and the occurrence of a leukemic phase at any time during the course of the disease. The median age is 59 but pediatric cases do exist. At the morphological level skin biopsy shows a monomorphous cell proliferation simulating a pleomorphic T cell cutaneous lymphoma. The diagnosis is based on phenotypic criteria which require frozen tissue. Currently, the main characteristics are the expression of CD4 and CD56 antigens while the main defined lineage specific markers are negative (B-cell, T-cell, NK-cell and myeloid-cell lineages). The origin of the tumor cells still remains uncertain but the plasmacytoid dendritic cell is presently a very serious candidate. The tumor cells share a great phenotypical homology and particularly the expression of the CD123 antigen. Functional homologies have also been demonstrated with tumor cells in vitro. Outcome of CD4/CD56 hematodermic neoplasms is very bad. The median time of survival is 14 months irrespective of the treatment given. Conventional chemotherapies used for the treatment of aggressive lymphomas or acute myeloid leukemias are quickly inefficient.