Fax +41 61 306 12 34 E-Mail karger@karger.ch www.karger.com Case Report Acta Haematol 2011;126:122–128 DOI: 10.1159/000328180 Blastic Plasmacytoid Dendritic Cell Neoplasm Expressing the CD13 Myeloid Antigen Daichi Inoue   a, e Kyoko Maruyama   d Kazunari Aoki   a Seiji Nagano   a Hayato Maruoka   b Yukihiro Imai   c Kiminari Ito   d Takayuki Ishikawa   a Takayuki Takahashi   a   a  Department of Hematology and Clinical Immunology, b  Clinical Laboratory, c  Department of Clinical Pathology, Kobe City Medical Center General Hospital, d  Department of Cell Therapy, Foundation of Biomedical Research and Innovation, Kobe, and e  Division of Cellular Therapy, Advanced Clinical Research Center, The Institute of Medical Science, The University of Tokyo, Tokyo, Japan this is the first report of BPDCN expressing a myeloid anti- gen, CD13, although CD33 expression has been described in some cases. The present patient received 2 courses of com- bination chemotherapy consisting of cytarabine and etopo- side, which resulted in complete remission. Given that the cellular origin of plasmacytoid DC is still controversial, my- eloid antigen expression involving CD13 may not exclude a diagnosis of BPDCN. Copyright © 2011 S. Karger AG, Basel Introduction Blastic plasmacytoid dendritic cell neoplasm (BPDCN), which is also known as agranular CD4+CD56+ hemato- dermic neoplasm or blastic natural killer cell lymphoma, is a rare and highly aggressive neoplasm that frequently manifests as cutaneous lesions, followed by dissemina- tion to the peripheral blood, bone marrow and lymph nodes [1–3]. BPDCN was initially supposed to be a natu- ral killer cell neoplasm [4]. However, it is currently be- lieved to originate from immature dendritic cells (DC), Key Words Antigen-presenting cells  Blastic plasmacytoid dendritic cell neoplasm  CD13  CD40 ligand  Dendritic cells  IL-3 Abstract Blastic plasmacytoid dendritic cell neoplasm (BPDCN), cur- rently considered to originate from immature plasmacytoid dendritic cells (DC), is a rare and aggressive CD4+CD56+ neoplasm that frequently involves the skin and bone mar- row. We present a case of an 80-year-old man with a CD4+CD56+ BPDCN that affected the orbital cavity and bone marrow. Although BPDCN has not been reported to express any lineage-specific markers, the neoplastic cells strongly expressed the CD13 antigen. Therefore, in addition to pathological examination, we attempted to induce in vi- tro morphological and surface marker changes with IL-3 and CD40 ligand. After treatment with these cytokines, the tu- mor cells enlarged markedly, acquired many fine dendrites, similar to mature DC, and showed enhanced expression of antigens specific to DC or antigen-presenting cells, such as CD40, CD80, CD83 and CD86. To the best of our knowledge, Received: February 7, 2011 Accepted after revision: April 5, 2011 Published online: June 24, 2011 Daichi Inoue Department of Hematology and Clinical Immunology Kobe City Medical Center General Hospital 4-6 Minatojima-Nakamachi, Chuo-ku, Kobe 650-0046 (Japan) Tel. +81 78 302 4321, E-Mail daichi-i  @  hotmail.co.jp © 2011 S. Karger AG, Basel 0001–5792/11/1262–0122$38.00/0 Accessible online at: www.karger.com/aha