CD56-positive haematological neoplasms of the skin: a multicentre study of the Cutaneous Lymphoma Project Group of the European Organisation for Research and Treatment of Cancer

Blastic Plasmocytoid Dendritic Cell Neoplasm (BPDCN): Clinical Features and Histopathology with a Therapeutic Overview

Blastic Plasmacytoid Dendritic Cell Neoplasms (BPDCNs) are a rare, highly aggressive hematological malignant neoplasm that primarily involve the skin, bone marrow, lymph nodes and even extra-nodal sites. The rarity and relative poor description of cases in the literature make it necessary to review and further studies that deeply investigate this entity not only in a histopathological but also molecular field. In August-September 2023, we searched MEDLINE, PubMed and Scopus for randomized controlled trials (RCTs), narrative and systematic reviews, meta-analyses, observational studies (either longitudinal or retrospective), and case series published in English in the last 25 years using the keywords BPDCN, PDCs, Blastic NK-cell lymphoma, agranular CD4+ NK leukemia/lymphoma, agranular CD4+ CD56+ hematodermic neoplasm/tumor. Despite the progress made in recent years in the diagnosis and biological understanding of the disease, until 2018 there was no clear consensus regarding its treatment and the main therapeutic schemes used were based on chemotherapy regimens already used in the treatment of lymphomas, acute lymphoblastic leukemia (ALL) and/or acute myeloid leukemia (AML). In this narrative review, we address the definition and epidemiological features of BPDCN, provide the different theories on the etiopathogenesis with particular attention to the presumed cell of origin, discuss the main clinical manifestations that provide a sign of its presence, summarize the main histopathological and immunophenotypic characteristics with special attention to the most important markers, and finally, we provide some of the most effective information on the therapeutic treatment modalities of BPDCN.

Blastic plasmacytoid dendritic cell neoplasm in an adolescent female: a rare entity with challenging diagnosis and management

Blastic plasmacytoid dendritic cell neoplasm is a rare and aggressive haematopoietic neoplasm with poor prognosis. It usually presents with cutaneous lesions and symptoms secondary to bone marrow involvement. Due to rarity and lack of standard treatment protocols, these cases are difficult to diagnose and treat. We report a case of a female in early adolescence who presented with skin nodules on the leg. The diagnosis was established by immunophenotypic studies. We discuss the investigations and treatment options available to diagnose and treat this malignancy.

Cutaneous Involvement of Extranodal NK/T Cell Lymphoma, Nasal Type, a Clinical and Histopathological Mimicker of Various Skin Diseases

Background: Extranodal NK/T cell lymphoma, nasal type (ENK/T) with cutaneous involvement has various histopathological findings and diverse clinical manifestations. Methods: A retrospective study of cutaneous involvement of ENK/T lymphoma between 2006 and 2018 was conducted. Results: Twenty-two cases were eligible for this study. Twelve cases could be proven as secondary cutaneous involvement by ENK/T lymphoma, while the remaining could not be confirmed as primary cutaneous ENK/T lymphoma. The histopathological patterns included dermal and subcutaneous nodular infiltration pattern in 11/22 cases (50%), lobular panniculitis pattern in 6/22 cases (27.3%), interface dermatitis pattern in 4/22 cases (18.2%), and granulomatous dermatitis pattern in 1/22 case (4.5%). The median follow-up was 18.3 months. Overall, the one-year and five-year survival rates were 31.3% and 13.3%, respectively. Conclusions: A variety of histopathological patterns of cutaneous involvement by ENK/T lymphoma should be differentiated from other cutaneous lymphomas, dermatitis, and infection. When atypical medium or large-sized lymphoid cells are encountered within skin lesions, pathologists should realize these lesions can be ENK/T lymphoma, especially in cases with coexisting tumor necrosis or angioinvasion. A complete evaluation of the upper aerodigestive tract is mandatory to identify the occult primary site of ENK/T lymphoma before establishing primary cutaneous ENK/T lymphoma.

Indispensable role of immunophenotyping in diagnosing leukemic phase of blastic plasmacytoid dendritic cell neoplasm without cutaneous manifestation

Blastic plasmacytoid dendritic cell neoplasm usually presents as skin lesions. Diagnostic error occurs when it primarily presents in leukemic phase without skin involvement. Triad of CD4, CD56 and CD123 immunophenotype expression is essential to avoid misdiagnosis of this rare hematological malignancy. Here we describe a patient who presented in overt leukemic phase of BPDCN highlighting diagnostic challenges encountered that resulted in delayed diagnosis and poor outcome.

Blastic Plasmacytoid Dendritic Cell Neoplasm: A Rare Case Report with Literature Review

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare hematopoietic neoplasm for which there are no effective therapies. We present a 70-year-old male patient with multiple reddish painless, nonpruritic, and nonpedunculated nodules over the trunk, forearm, and thighs for a duration of 3 months. The nodules measured 0.5 to 2 cm in diameter. The peripheral smear findings were within normal limits. Excision biopsy was performed. Histomorphology and immunohistochemistry (CD123, CD 56, CD4, HLA-DR, CD43, and CD68) confirmed the diagnosis of BPDCN. Findings of marrow aspiration, biopsy and imaging studies were within normal limits. Patient demonstrated a good response with complete disappearance of all nodules by initial 2 weeks of therapy with a modified Berlin–Frankfurt–Munster (BFM) acute lymphoblastic leukemia (ALL) protocol and has completed 8 doses (LSAP [lincosamides, streptogramins A and pleuromutilins chemotherapy], 5,000 units/m2). The patient tolerated protocol extremely well.

Newly-Discovered Neural Features Expand the Pathobiological Knowledge of Blastic Plasmacytoid Dendritic Cell Neoplasm

Simple Summary

For the first time, neuronal features are described in blastic plasmacytoid dendritic cell neoplasm (BPDCN) by a complex array of molecular techniques, including microRNA and gene expression profiling, RNA and Chromatin immunoprecipitation sequencing, and immunohistochemistry. The discovery of unexpected neural features in BPDCN may change our vision of this disease, leading to the designing of a new BPDCN cell model and to re-thinking the relations occurring between BPDCN and nervous system. The observed findings contribute to explaining the extreme tumor aggressiveness and also to propose novel therapeutic targets. In view of this, the identification, in this work of new potential neural metastatic inducers might open the way to therapeutic approaches for BPDCN patients based on the use of anti-neurogenic agents.

Abstract

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare and highly aggressive hematologic malignancy originating from plasmacytoid dendritic cells (pDCs). The microRNA expression profile of BPDCN was compared to that of normal pDCs and the impact of miRNA dysregulation on the BPDCN transcriptional program was assessed. MiRNA and gene expression profiling data were integrated to obtain the BPDCN miRNA-regulatory network. The biological process mainly dysregulated by this network was predicted to be neurogenesis, a phenomenon raising growing interest in solid tumors. Neurogenesis was explored in BPDCN by querying different molecular sources (RNA sequencing, Chromatin immunoprecipitation-sequencing, and immunohistochemistry). It was shown that BPDCN cells upregulated neural mitogen genes possibly critical for tumor dissemination, expressed neuronal progenitor markers involved in cell migration, exchanged acetylcholine neurotransmitter, and overexpressed multiple neural receptors that may stimulate tumor proliferation, migration and cross-talk with the nervous system. Most neural genes upregulated in BPDCN are currently investigated as therapeutic targets.

Clinicopathological and prognostic study of primary cutaneous extranodal natural killer/T-cell lymphoma, nasal type: A systematic review

Comprehensive studies of primary cutaneous extranodal natural killer/T-cell lymphoma (PCENKTL) are scarce. The objectives of this study are to describe PCENKTL in terms of its clinical features, histopathology, immunophenotypes, and prognosis, and to analyze factors affecting patient survival outcomes. We searched four databases and include studies with extractable data. We also searched the Asan Medical Center database for cases of PCENKTL. We include a total of 289 patients. The mean age at diagnosis was 52.8 years and the female to male ratio was 1:1.2. The most common clinical morphology was a subcutaneous nodule, followed by ulceration. About half of the patients presented with disseminated skin lesions. The median overall survival was 12.0 months and the 5-year survival rate was 22.0%. There was no correlation between the clinical morphology or the histopathological features of the skin lesions with the patient outcomes. Advanced TNM stage, a disseminated skin lesion, tumor location on the leg or trunk, the presence of B symptoms, and a high International Prognostic Index score were associated with a worse prognosis, and chemoradiotherapy was associated with a better survival outcome as compared with chemotherapy alone in univariable analyses. In multivariable analyses, only advanced TNM stage and tumor location on the leg were associated with a worse prognosis. In conclusion, PCENKTL is an aggressive cutaneous lymphoma and its prognosis is associated with TNM stage and tumor location.

Blastic Plasmacytoid Dendritic Cell Neoplasm: State of the Art and Prospects

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is an extremely rare tumour, which usually affects elderly males and presents in the skin with frequent involvement of the bone-marrow, peripheral blood and lymph nodes. It has a dismal prognosis, with most patients dying within one year when treated by conventional chemotherapies. The diagnosis is challenging, since neoplastic cells can resemble lymphoblasts or small immunoblasts, and require the use of a large panel of antibodies, including those against CD4, CD56, CD123, CD303, TCL1, and TCF4. The morphologic and in part phenotypic ambiguity explains the uncertainties as to the histogenesis of the neoplasm that led to the use of various denominations. Recently, a series of molecular studies based on karyotyping, gene expression profiling, and next generation sequencing, have largely unveiled the pathobiology of the tumour and proposed the potentially beneficial use of new drugs. The latter include SL-401, anti-CD123 immunotherapies, venetoclax, BET-inhibitors, and demethylating agents. The epidemiologic, clinical, diagnostic, molecular, and therapeutic features of BPDCN are thoroughly revised in order to contribute to an up-to-date approach to this tumour that has remained an orphan disease for too long.

Kutane Lymphome

Kutane Lymphome (cutaneous lymphomas: CL) umfassen die Gruppe der kutanen T-Zell-Lymphome (cutaneous T-cell lymphomas: CTCL), kutanen B-Zell-Lymphome (cutaneous B-cell lymphomas: CBCL) und die sog. hämatodermischen Neoplasien (HN). CL gehören zur Gruppe der Non-Hodgkin-Lymphome (NHL) und stellen in der Subgruppe der extranodalen NHL die zweithäufigste Gruppe hinter den gastrointestinalen Lymphomen dar (Jaffe et al. 2009). Man unterscheidet zwischen primären und sekundären CL. Primäre CL haben ihren Ursprung in der Haut und bleiben in der Regel darauf auch längere Zeit beschränkt, während sekundäre CL kutane Manifestationen von primär nodalen oder extranodalen Lymphomen darstellen (Willemze 2005). Die primären CL unterscheiden sich hinsichtlich klinischem Verlauf, Therapieoptionen und Prognose erheblich von nodalen und extrakutanen Lymphomen. So zeigen z. B. die primär kutanen CD30+-T-Zell-Lymphome einen gutartigen Verlauf, wogegen die nodalen Varianten als aggressiv eingestuft werden. Da die CL zumeist weniger aggressiv sind, werden sie auch weniger aggressiv behandelt.

Cutaneous presentation preceding acute myeloid leukemia with CD4+/CD56+ expression misdiagnosed as a blastic plasmocytoid dendritic cell neoplasm: A case report

Acute myeloid leukemia (AML) may initially present as cutaneous lesions corresponding to blasts involving the skin as the first clinical manifestation prior to blood and bone marrow (BM) infiltration. Such presentation is known as myeloid leukemia cutis (LC). Blastic plasmocytoid dendritic cell neoplasm (BPDCN) is an aggressive tumor derived from the precursors of plasmocytoid dendritic cells with cutaneous and BM involvement and leukemic dissemination. Myeloid LC and BPDCN may be difficult to distinguish as they share similar clinical and histopathological features, in particular AML with monocytic differentiation. Nevertheless, the correct diagnosis has to be made to determine adequate and effective therapy. Here, we report the case of a 61-year-old woman who presented with an AML with MLL rearrangement and CD4+/CD56+ expression presenting as LC and that was misdiagnosed as BPDCN. We emphasize that careful and exhaustive analyses should be performed to make the correct diagnosis.

Atypical presentation of blastic plasmacytoid dendritic cell neoplasm: A potential diagnostic pitfall in nasal cavity

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare disease with an aggressive clinical course resulting in median survival times of 12 to 14 months.¹ It represents approximately 0.8% of primary cutaneous lymphomas.² According to the World Health Organization Classification of Tumors of Hematopoietic and Lymphoid Tissue, published in 2008, BPDCN is defined as an acute myeloid leukemia related precursor neoplasm, derived from precursors of the plasmacytoid dendritic cell. It is characterized microscopically by its dense monomorphous infiltrates of medium-sized blastoid morphology and expression of CD4 and CD56, as well as the absence of any common myeloid, T-lymphoid, B-lymphoid, and natural killer-lymphoid lineage markers.³ A few series of BPDCN have been reported in the literature, but very few cases of BPDCN have been described with lack of skin manifestation at the time of diagnosis.⁴ Here, we report a rare case of BPDCN in the nasal cavity.

Improved in vitro and in vivo activity against CD303-expressing targets of the chimeric 122A2 antibody selected for specific glycosylation pattern

Plasmacytoid dendritic cells (pDCs) play a central role for both innate and adaptive antiviral responses, as they direct immune responses through their unique ability to produce substantial concentrations of type I interferon (IFNs) upon viral encounter while also activating multiple immune cells, including macrophages, DCs, B, natural killer and T cells. Recent evidence clearly indicates that pDCs also play a crucial role in some cancers and several auto-immune diseases. Although treatments are currently available to patients with such pathologies, many are not fully efficient. We are proposing here, as a new targeted-based therapy, a novel chimeric monoclonal antibody (mAb) that mediates a strong cellular cytotoxicity directed against a specific human pDC marker, CD303. This antibody, ch122A2 mAb, is characterized by low fucose content in its human IgG1 constant (Fc) region, which induces strong in vitro and in vivo activity against human pDCs. We demonstrated that this effect relates in part to its specific Fc region glycosylation pattern, which increased affinity for CD16/FcγRIIIa. Importantly, ch122A2 mAb induces the down-modulation of CpG-induced IFN-α secretion by pDCs. Additionally, ch122A2 mAb shows in vitro high pDC depletion mediated by antibody-dependent cell-mediated cytotoxicity and antibody-dependent cellular phagocytosis. Remarkably, in vivo ch122A2 mAb efficacy is also demonstrated in humanized mice, resulting in significant pDC depletion in bloodstream and secondary lymphoid organs such as spleen. Together, our data indicates that ch122A2 mAb could represent a promising cytotoxic mAb candidate for pathologies in which decreasing type I IFNs or pDCs depleting may improve patient prognosis.

B-cell Lymphofollicular Infiltrates in Mycosis Fungoides

Aims and background

The histopathological picture of mycosis fungoides can be characterized by heavy reactive infiltrates. These are rarely composed of B lymphocytes with formation of reactive follicles.

Methods and study design

We collected three cases of mycosis fungoides with a reactive B-cell lymphofollicular reaction at the bottom of the epidermotropic infiltrate.

Results

Case 1 showed flat lesions (patches) with a CD4+ neoplastic phenotype; case 2 presented infiltrated lesions (plaques) with a CD8+ immonophenotype; case 3 was characterized by nodular lesions (tumors) with a CD4+ neoplastic component. In all three cases, no clonal gene rearrangement was found with the polymerase chain reaction technique.

Conclusions

Among the protean clinicopathological features which mycosis fungoides can show, we underline that a B-cell lymphofollicular component can be encountered at the base of the epidermotropic infiltrate even in clinically flat (“patchy”) lesions.

Blastic plasmacytoid dendritic cell neoplasm: challenges and future prospects

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare CD4+ CD56+ myeloid malignancy that is challenging to diagnose and treat. BPDCN typically presents with nonspecific cutaneous lesions with or without extra-cutaneous manifestations before progressing to leukemia. Currently, there is no standard of care for the treatment of BPDCN and various approaches have been used including acute myeloid leukemia, acute lymphoblastic leukemia, and lymphoma-based regimens with or without stem cell transplantation. Despite these treatment approaches, the prognosis of BPDCN remains poor and there is a lack of prospective data upon which to base treatment decisions. Recent work examining the mutational landscape and gene expression profiles of BPDCN has identified a number of potential therapeutic targets. One such target is CD123, the α subunit of the human interleukin-3 receptor, which is the subject of intervention studies using the novel agent SL-401. Other investigational therapies include UCART123, T-cell immunotherapy, and venetoclax. Prospective trials are needed to determine the best treatment for this uncommon and aggressive neoplasm.

[Treatment of rare cutaneous T‑cell lymphoma and blastic plasmacytoid dendritic cell neoplasm]

Among the group of primary cutaneous lymphomas several subtypes have very low incidence rates. Based on the revision of the WHO classification for lymphoid neoplasms (2016), an overview of rare cutaneous T‑cell lymphoma (CTCL) subtypes is given and therapeutic approaches are detailed. The prognosis of the different subtypes is highly variable underlining the importance of adequate stage and subtype adapted treatment. In cases of indolent subtypes topical treatment, e. g. topical corticosteroids or UV phototherapy are often sufficient. For aggressive variants, early discussion of more aggressive systemic treatment options is warranted.

Evaluation of CD43 expression in non-hematopoietic malignancies

OBJECTIVES

CD43 is normally expressed only on the surface of leukocytes, and is considered a sensitive and specific marker for hematologic malignancies. As such, it may have diagnostic utility in confirming hematolymphoid lineage in cases that are negative for CD45. Aberrant CD43 expression has been described in non-hematopoietic tumors, although literature data on this topic is variable and sometimes contradictory. To clarify and expand on existing literature findings, we evaluated CD43 expression by immunohistochemistry (IHC) in a large cohort (307) of non-hematopoietic neoplasms, including poorly differentiated malignancies.

METHODS

17 tissue microarrays and sections from 19 individual cases were stained with CD43 (clone DF-T1) monoclonal antibody. The proportion of positive cells, stain localization (nuclear, cytoplasmic or membranous), and intensity (compared to internal leukocyte controls) were recorded in all cases.

RESULTS

There were 98/307 (32%) positive cases, that showed focal weak nuclear staining in 1-25% of cells, including 23/25 (92%) pancreatic ductal adenocarcinomas; 31/34 (91%) breast invasive ductal carcinomas; 13/15 (87%) papillary thyroid carcinomas; 3/4 (75%) follicular thyroid carcinomas; 6/15 (40%) renal cell carcinomas; 9/28 (32%) lung adenocarcinomas; 1/13 (8%) lung squamous cell carcinomas (SCCs); 2/8 (25%) prostate adenocarcinomas; 8/62 (13%) colon adenocarcinomas; and 2/21 (10%) neuroendocrine neoplasms. None of the positive cases demonstrated strong, membranous CD43 expression comparable to that seen in background mature lymphocytes or segmented neutrophils. Negative cases included 11 cervical SCCs, 12 cervical adenocarcinomas, 19 urothelial carcinomas, 10 lung small cell carcinomas, 11 sarcomas, and 19 poorly differentiated carcinomas from various tissue sites.

CONCLUSIONS

In our cohort, most non-hematopoietic neoplasms are negative for CD43 expression, with a subset showing focal, weak nuclear positivity. This data indicates that uniform and strong membranous staining appears to be specific to hematopoietic neoplasms.

A Case of Blastic Plasmacytoid Dendritic Cell Neoplasm Extensively Studied by Flow Cytometry and Immunohistochemistry

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare hematologic malignancy with aggressive clinical course and poor prognosis. Diagnosis is based on detection of CD4⁺ CD56⁺, CD123^high, TCL-1⁺, and blood dendritic cell antigen-2/CD303⁺ blasts, together with the absence of lineage specific antigens on tumour cells. In this report we present a case of BPDCN presenting with extramedullary and bone marrow involvement, extensively studied by flow cytometry and immunohistochemistry, who achieved complete remission after acute lymphoblastic leukemia like chemotherapy and allogeneic hematopoietic stem cell transplantation.

Diagnostic value of 18F-FDG PET/CT for cutaneous extranodal natural killer/T-cell lymphoma, nasal type

OBJECTIVE

To evaluate the use of fluorine-18 fluorodeoxyglucose (F-FDG) PET/computed tomography (CT) in the diagnosis of cutaneous extranodal natural killer/T-cell lymphoma, nasal type (C-ENK/T-NT).

METHODS

A total of 39 patients with newly diagnosed C-ENK/T-NT were enrolled between May 2006 and November 2013. Anatomic regions (n=429; five cutaneous and six extracutaneous regions per patient) were assessed using an F-FDG PET/CT scan and conventional staging methods (CSMs). F-FDG PET/CT and CSMs were compared and evaluated for their ability to detect tumor lesions and their influence on the staging and treatment strategies. Biopsy and clinical follow-up were used as the gold standard for diagnosis.

RESULTS

In total, 139 lesions were detected by CSMs and F-FDG PET/CT, of which there were 50 cutaneous and 89 extracutaneous-positive regions. F-FDG PET/CT detected 48 cutaneous and 88 extracutaneous regions. CSMs, however, detected only 34 cutaneous lesions and 61 extracutaneous lesions that were positive for malignancy (cutaneous comparison of PET/CT vs. CSMs, P<0.001; extracutaneous comparison of PET/CT vs. CSMs, P<0.05). Using F-FDG PET/CT, 8 (42%) patients were in stage I-II and 31 patients (58%) were in stage III-IV. F-FDG PET/CT staging was consistent with the final stage determination in 94.9% (37/39) of patients, whereas CSMs staging was correct in final stage determination in 74.4% (29/39) of patients (P=0.025).

CONCLUSION

Our study showed that F-FDG PET/CT scanning is a valuable modality for the detection of cutaneous and extracutaneous lesions of C-ENK/T-NT. F-FDG PET/CT may therefore influence future staging and treatment strategies.

A Druggable TCF4- and BRD4-Dependent Transcriptional Network Sustains Malignancy in Blastic Plasmacytoid Dendritic Cell Neoplasm

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is an aggressive and largely incurable hematologic malignancy originating from plasmacytoid dendritic cells (pDCs). Using RNAi screening, we identified the E-box transcription factor TCF4 as a master regulator of the BPDCN oncogenic program. TCF4 served as a faithful diagnostic marker of BPDCN, and its downregulation caused the loss of the BPDCN-specific gene expression program and apoptosis. High-throughput drug screening revealed that bromodomain and extra-terminal domain inhibitors (BETis) induced BPDCN apoptosis, which was attributable to disruption of a BPDCN-specific transcriptional network controlled by TCF4-dependent super-enhancers. BETis retarded the growth of BPDCN xenografts, supporting their clinical evaluation in this recalcitrant malignancy.

Neoplasms derived from plasmacytoid dendritic cells

Plasmacytoid dendritic cell neoplasms manifest in two clinically and pathologically distinct forms. The first variant is represented by nodular aggregates of clonally expanded plasmacytoid dendritic cells found in lymph nodes, skin, and bone marrow ('Mature plasmacytoid dendritic cells proliferation associated with myeloid neoplasms'). This entity is rare, although likely underestimated in incidence, and affects predominantly males. Almost invariably, it is associated with a myeloid neoplasm such as chronic myelomonocytic leukemia or other myeloid proliferations with monocytic differentiation. The concurrent myeloid neoplasm dominates the clinical pictures and guides treatment. The prognosis is usually dismal, but reflects the evolution of the associated myeloid leukemia rather than progressive expansion of plasmacytoid dendritic cells. A second form of plasmacytoid dendritic cells tumor has been recently reported and described as 'blastic plasmacytoid dendritic cell neoplasm'. In this tumor, which is characterized by a distinctive cutaneous and bone marrow tropism, proliferating cells derive from immediate CD4(+)CD56(+) precursors of plasmacytoid dendritic cells. The diagnosis of this form can be easily accomplished by immunohistochemistry, using a panel of plasmacytoid dendritic cells markers. The clinical course of blastic plasmacytoid dendritic cell neoplasm is characterized by a rapid progression to systemic disease via hematogenous dissemination. The genomic landscape of this entity is currently under intense investigation. Recurrent somatic mutations have been uncovered in different genes, a finding that may open important perspectives for precision medicine also for this rare, but highly aggressive leukemia.

Cutaneous squamous and neuroendocrine carcinoma: genetically and immunohistochemically different from Merkel cell carcinoma

Cutaneous neuroendocrine (Merkel cell) carcinoma most often arises de novo in the background of a clonally integrated virus, the Merkel cell polyomavirus, and is notable for positive expression of retinoblastoma 1 (RB1) protein and low expression of p53 compared with the rare Merkel cell polyomavirus-negative Merkel cell carcinomas. Combined squamous and Merkel cell tumors are consistently negative for Merkel cell polyomavirus. Little is known about their immunophenotypic or molecular profile. Herein, we studied 10 combined cutaneous squamous cell and neuroendocrine carcinomas for immunohistochemical expression of p53, retinoblastoma 1 protein, neurofilament, p63, and cytokeratin 20 (CK20). We compared mutation profiles of five combined Merkel cell carcinomas and seven 'pure' Merkel cell carcinomas using targeted next-generation sequencing. Combined tumors were from the head, trunk, and leg of Caucasian males and one female aged 52-89. All cases were highly p53- and p63-positive and neurofilament-negative in the squamous component, whereas RB1-negative in both components. Eight out of 10 were p53-positive, 3/10 p63-positive, and 3/10 focally neurofilament-positive in the neuroendocrine component. Six out of 10 were CK20-positive in any part. By next-generation sequencing, combined tumors were highly mutated, with an average of 48 mutations per megabase compared with pure tumors, which showed 1.25 mutations per megabase. RB1 and p53 mutations were identified in all five combined tumors. Combined tumors represent an immunophenotypically and genetically distinct variant of primary cutaneous neuroendocrine carcinomas, notable for a highly mutated genetic profile, significant p53 expression and/or mutation, absent RB1 expression in the context of increased RB1 mutation, and minimal neurofilament expression.

Blastic plasmacytoid dendritic cell neoplasm: update on molecular biology, diagnosis, and therapy

BACKGROUND

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare hematological malignancy with an aggressive clinical course. Most patients with BPDCN have skin lesions and simultaneous involvement of the peripheral blood, bone marrow, and lymph nodes.

METHODS

A search of PubMed and Medline was conducted for English-written articles relating to BPDCN, CD4(+)CD56(+) hematodermic neoplasm, and blastic natural killer cell lymphoma. Data regarding diagnosis, prognosis, and treatment were analyzed.

RESULTS

BPDCN is derived from precursor plasmacytoid dendritic cells. The diagnosis of BPDCN is based on the characteristic cytology and immunophenotype of malignant cells coexpressing CD4, CD56, CD123, blood dendritic cell antigens 2 and 4, and CD2AP markers. Multiple chromosomal abnormalities and gene mutations previously reported in patients with myeloid and selected lymphoid neoplasms were identified in approximately 60% of patients with BPDCN. Prospectively controlled studies to guide treatment decisions are lacking. The overall response rate with aggressive acute lymphoblastic leukemia-type induction regimens was as high as 90%, but the durability of response was short. Median survival rates ranged between 12 and 16 months. Patients with relapsed disease may respond to L-asparaginase-containing regimens. Allogeneic hematopoietic stem cell transplantation, particularly when performed during the first remission, may produce durable remissions in selected adults.

CONCLUSIONS

BPDCN is a rare aggressive disease that typically affects elderly patients. The most commonly affected nonhematopoietic organ is the skin. Although BPDCN is initially sensitive to conventional chemotherapy regimens, this response is relatively short and long-term prognosis is poor. In the near future, novel targeted therapies may improve outcomes for patients with BPDCN.

Blast phase in chronic myelogenous leukemia is skewed toward unusual blast types in patients treated with tyrosine kinase inhibitors: a comparative study of 67 cases

OBJECTIVES

To compare the features of the blast phase of chronic myelogenous leukemia (CML) in patients treated with tyrosine kinase inhibitors (TKIs) with those in the pre-TKI era.

METHODS

Sixty-seven patients with blast phase CML were identified in the Duke Pathology database from 1991 to 2011. The morphology and immunophenotype of blasts were evaluated, along with cytogenetic studies and associated findings in the peripheral blood and bone marrow.

RESULTS

In the TKI era, the blasts were more frequently of a type other than the usual myeloid or lymphoid types when compared with the pre-TKI era. Blast phase in TKI-treated patients was associated with a higher peripheral WBC count and a lower blast percentage in the bone marrow. Of the 23 patients with cytogenetic studies during blast phase, additional cytogenetic changes more frequently occurred in patients with an unusual blast type, and some patients showed these changes months before the onset of blast phase.

CONCLUSIONS

Blast phase CML in TKI- and non-TKI-treated patients differs in the morphology and immunophenotype of blasts, cytogenetic findings, and associated findings in the peripheral blood and bone marrow.

Blastic plasmacytoid dendritic cell neoplasm presenting with a cutaneous tumor alone as the first symptom of onset: A case report and review of literature

Blastic plasmacytoid dendritic cell neoplasm (BPDCN), formerly named cluster of differentiation (CD)4⁺/CD56⁺ haematodermic neoplasm or blastic natural killer cell lymphoma, is a rare and highly aggressive haematopoietic malignancy. BPDCN typically occurs in the elderly, with a marked predilection for cutaneous involvement. The present study describes a case of BPDCN occurring in a 79-year-old male. The patient presented with skin lesions alone, with no evidence of extracutaneous involvement during the course of the disease. BPDCN was diagnosed based on histological and immunohistochemical observations and the patient was subsequently treated with local radiotherapy alone. However, rapid disease progression occurred and the patient succumbed five months after being diagnosed. The current result therefore demonstrated that BPDCN is highly aggressive even without systemic dissemination, and that radiotherapy appears to be ineffective in treating this tumor. The present study emphasizes the importance of pathologists and dermatologists being aware of this uncommon disease in order to avoid misdiagnosis.

Blastic plasmacytoid dendritic cell neoplasm: a clinicopathologic review

Blastic plasmacytoid dendritic cell neoplasm is a rare entity grouped with the acute myeloid leukemia-related precursor neoplasms in the 2008 World Health Organization classification. It was previously postulated to originate from natural killer cells, T cells, or monocytes but is now believed to arise from the plasmacytoid dendritic cell. The pathogenesis of blastic plasmacytoid dendritic cell neoplasm is not well understood, although the neoplasm demonstrates frequent deletion of tumor suppressor genes, including RB1, CDKN1B, CDKN2A, and TP53. Blastic plasmacytoid dendritic cell neoplasm is a clinically aggressive tumor that often initially presents as cutaneous lesions and subsequently progresses to bone marrow involvement and leukemic dissemination. It is characterized by enhanced expression of CD56, CD4, and CD123, which can be detected by flow cytometry/immunohistochemistry. The differential diagnoses include myeloid sarcoma/acute myeloid leukemia, T-cell lymphoblastic leukemia/lymphoma, NK-cell lymphoma/leukemia, and some mature T-cell lymphomas/leukemias. Patients usually respond to initial chemotherapy but often relapse. Stem cell transplant may improve survival.

Expression of CD31/PECAM-1 (platelet endothelial cell adhesion molecule 1) by blastic plasmacytoid dendritic cell neoplasms

IMPORTANCE

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare malignant neoplasm with cutaneous manifestations and a rapidly progressive clinical course. The diagnosis relies on characteristic clinicopathologic and immunopathologic features. However, the overlap of immunophenotypic features with other cancers, as well as newly discovered interpersonal and intrapersonal phenotypic variations, renders the identification of BPDCN challenging. A greater understanding of the proteins expressed by BPDCN might facilitate its recognition and provide insights into its clinical behavior.

OBSERVATIONS

In 7 of 9 patients at 4 tertiary care institutions, immunohistochemical analysis demonstrated strong CD31/PECAM-1 (platelet endothelial cell adhesion molecule 1) expression by neoplastic cells. Combined with similar findings observed in 1 former patient, 8 of 10 cases of BPDCN were CD31/PECAM-1 positive.

CONCLUSIONS AND RELEVANCE

Expression of CD31/PECAM-1 by BPDCN adds new information about the antigenic profile of this unusual neoplasm. CD31/PECAM-1 influences multiple cell functions including adhesion, apoptosis, coagulation, host response, and protein synthesis that might affect clinical features of BPDCN such as hemorrhage, aggressive tumor growth, and resistance to therapy. Therefore, the potential role of this molecule in the tumor formation and progression of BPDCN warrants additional exploration.

Molecular profiling of blastic plasmacytoid dendritic cell neoplasm reveals a unique pattern and suggests selective sensitivity to NF-kB pathway inhibition

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare disease of controversial origin recently recognized as a neoplasm deriving from plasmacytoid dendritic cells (pDCs). Nevertheless, it remains an orphan tumor with obscure biology and dismal prognosis. To better understand the pathobiology of BPDCN and discover new targets for effective therapies, the gene expression profile (GEP) of 25 BPDCN samples was analyzed and compared with that of pDCs, their postulated normal counterpart. Validation was performed by immunohistochemistry (IHC), whereas functional experiments were carried out ex vivo. For the first time at the molecular level, we definitely recognized the cellular derivation of BPDCN that proved to originate from the myeloid lineage and in particular, from resting pDCs. Furthermore, thanks to an integrated bioinformatic approach we discovered aberrant activation of the NF-kB pathway and suggested it as a novel therapeutic target. We tested the efficacy of anti-NF-kB-treatment on the BPDCN cell line CAL-1, and successfully demonstrated by GEP and IHC the molecular shutoff of the NF-kB pathway. In conclusion, we identified a molecular signature representative of the transcriptional abnormalities of BPDCN and developed a cellular model proposing a novel therapeutic approach in the setting of this otherwise incurable disease.

Kutane Lymphome

Kutane Lymphome (cutaneous lymphomas: CL) umfassen die Gruppe der kutanen T-Zell-Lymphome (cutaneous T-cell lymphomas: CTCL), kutanen B-Zell-Lymphome (cutaneous B-cell lymphomas: CBCL) und die sog. hämatodermischen Neoplasien (HN). CL gehören zur Gruppe der Non-Hodgkin-Lymphome (NHL) und stellen in der Subgruppe der extranodalen NHL die zweithäufigste Gruppe hinter den gastrointestinalen Lymphomen dar (Jaffe et al. 2009). Man unterscheidet zwischen primären und sekundären CL. Primäre CL haben ihren Ursprung in der Haut und bleiben in der Regel darauf auch längere Zeit beschränkt, während sekundäre LymphomekutaneCL kutane Manifestationen von primär nodalen oder extranodalen Lymphomen darstellen (Willemze 2005). Die primären CL unterscheiden sich hinsichtlich klinischem Verlauf, Therapieoptionen und Prognose erheblich von nodalen und extrakutanen Lymphomen. So zeigen z. B. die primär kutanen CD30⁺ Lymphome einen gutartigen Verlauf, wogegen die nodalen Varianten als aggressiv eingestuft werden. Da die CL zumeist weniger aggressiv sind, werden sie weniger aggressiv behandelt.

Exome sequencing reveals novel and recurrent mutations with clinical impact in blastic plasmacytoid dendritic cell neoplasm

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a very rare disease that currently lacks genomic and genetic biomarkers to assist in its clinical management. We performed whole-exome sequencing (WES) of three BPDCN cases. Based on these data, we designed a resequencing approach to identify mutations in 38 selected genes in 25 BPDCN samples. WES revealed 37-99 deleterious gene mutations per exome with no common affected genes between patients, but with clear overlap in terms of molecular and disease pathways (hematological and dermatological disease). We identified for the first time deleterious mutations in IKZF3, HOXB9, UBE2G2 and ZEB2 in human leukemia. Target sequencing identified 29 recurring genes, ranging in prevalence from 36% for previously known genes, such as TET2, to 12-16% for newly identified genes, such as IKZF3 or ZEB2. Half of the tumors had mutations affecting either the DNA methylation or chromatin remodeling pathways. The clinical analysis revealed that patients with mutations in DNA methylation pathway had a significantly reduced overall survival (P=0.047). We provide the first mutational profiling of BPDCN. The data support the current WHO classification of the disease as a myeloid disorder and provide a biological rationale for the incorporation of epigenetic therapies for its treatment.

NK-/T-cell lymphoma resembling hydroa vacciniforme with positive CD4 marker expression: a diagnostic difficulty

A 35-year-old Chinese woman presented with a 2.5-year history of facial swelling in the left lower quadrant and a 10-month history of relapsing red papules and vesicles in the perioral area resembling hydroa vacciniforme. Histologically, a tissue biopsy showed a dense infiltration of medium-sized atypical lymphocytic cells expressing CD4 and CD56. A diagnosis of cutaneous NK-/T-cell lymphoma was made. The patient was treated with alpha-interferon, valaciclovir hydrochloride, and low-dose prednisone for 2 months. Her skin lesions and lymphoadenopathy resolved initially, but she succumbed to the disease shortly after starting chemotherapy treatment 11 months later. To our knowledge, this is the first case of CD4CD56 NK-/T-cell lymphoma with clinical features resembling hydroa vacciniforme.

Stem cell transplantation can provide durable disease control in blastic plasmacytoid dendritic cell neoplasm: a retrospective study from the European Group for Blood and Marrow Transplantation

Patients with blastic plasmacytoid dendritic cell neoplasm (BPDCN) have a poor prognosis with conventional chemotherapy. In the present study, we retrospectively analyzed the outcome of patients with BPDCN who underwent allogeneic stem cell transplantation (allo-SCT) or autologous stem cell transplantation (auto-SCT). A total of 39 patients (allo-SCT, n = 34; auto-SCT, n = 5) were identified in the European Group for Blood and Marrow Transplantation registry. The 34 allo-SCT patients had a median age of 41 years (range, 10-70) and received transplantations from sibling (n = 11) or unrelated donors (n = 23) between 2003 and 2009. MAC was used in 74% of patients. Nineteen allo-SCT patients (56%) received transplantations in first complete remission. The 3-year cumulative incidence of relapse, disease-free survival, and overall survival was 32%, 33%, and 41%, respectively. By univariate comparison, being in first remission at allo-SCT favorably influenced survival, whereas age, donor source, and chronic GVHD had no significant impact. We conclude that high-dose therapy followed by allo-SCT from related or unrelated donors can provide durable remission even in elderly patients with BPDCN. However, it remains to be shown if graft-versus-malignancy effects can contribute significantly to BPDCN control after allo-SCT.

Extranodal NK/T-cell lymphoma, nasal type, includes cases of natural killer cell and αβ, γδ, and αβ/γδ T-cell origin: a comprehensive clinicopathologic and phenotypic study

Extranodal NK/T-cell lymphoma (ENKTL), nasal type, may be of NK or T-cell origin; however, the proportion of T-ENKTLs and whether they are of αβ or γδ type remains uncertain. To elucidate the cell of origin and detailed phenotype of ENKTL and assess any clinicopathologic associations, 67 cases of ENKTL from Thailand were investigated, together with 5 γδ enteropathy-associated T-cell lymphomas (EATLs) for comparison. In all, 70% of the ENKTL were T-cell receptor (TCR) β,γ and, in cases tested, δ negative (presumptive NK origin); 5% were TCR γδ, 3% were TCR αβ, 1% were TCR αβ/γδ, and 21% were indeterminate. Out of 17 presumptive NK-ENKTLs tested, 3 had clonal TCR rearrangements. All cases were EBV and TIA-1; >85% were positive for CD3, CD2, granzyme B, pSTAT3, and Lsk/MATK; and all were CD16. Presumptive NK-ENKTLs had significantly more frequent CD56 (83% vs. 33%) and CXCL13 (59% vs. 0%) but less frequent PD-1 (0% vs. 40%) compared with T-ENKTLs. Of the NK-ENKTLs, 38% were Oct-2 compared with 0% of T-ENKTLs, and 54% were IRF4/MUM1 compared with 20% of T-ENKTLs. Only αβ T-ENKTLs were CD5. Intestinal ENKTLs were EBV and had significantly more frequent CD30, pSTAT3, and IRF4/MUM1 expression but less frequent CD16 compared with γδ EATL. Significant adverse prognostic indicators included a primary non-upper aerodigestive tract site, high stage, bone marrow involvement, International Prognostic Index ≥2, lack of radiotherapy, Ki67 >40%, and CD25 expression. The upper aerodigestive tract ENKTLs of T-cell origin compared with those of presumptive NK origin showed a trend for better survival. Thus, at least 11% of evaluable ENKTLs are of T-cell origin. Although T-ENKTLs have phenotypic and some possible clinical differences, they share many similarities with ENKTLs that lack TCR expression and are distinct from intestinal γδ EATL.