CD4(+)/CD56(+) Hematodermic (plasmacytoid dendritic cell) Tumor: a Highly Proliferating Neoplasm with Aberrant Expression of Immunohistochemical Markers and Poor Outcome.
Authors: Siakantaris Marina , Rassidakis George , Kontopidou Flora , Dimitrakopoulou Aglaia , Vassilakopoulos Theodoros , Angelopoulou Maria K. , Kokkoris Styliani , Evangelatos Nikolaos , Anargyrou Konstantinos , Michail Othon , Korkolopoulou Penelope , Pangalis G.A. 
Published: October 2019

Abstract
Abstract 2930
Poster Board II-906

Introduction:
CD4(+)/CD56(+) hematodermic (plasmacytoid dendritic cell) tumor is a rare, distinct clinico-pathologic entity according to the latest WHO/EORTC classification for cutaneous lymphomas. Skin is typically involved at presentation followed by lymph node and bone marrow involvement and often terminating in a leukemic phase. There is no standard treatment and the prognosis remains poor. Also, there is need for identification of prognostic markers, which will better stratify these patients. Recent data show that CD4(+)/CD56(+) hematodermic neoplasms express precursor dendritic cell related antigens such as CD123, BDCA-2, and TCL1 and CLA.

Patients:
Ten patients (8 men, 2 women) with a median age of 72.5 years (31-86) were included in the study. They presented with cutaneous lesions plaques, nodules or tumors. Three patients had also lymphadenopathy, 3 blood leukemic picture and 4 bone marrow involvement.

Results:
Histological features were consistent with medium sized blastic cell lymphoma. Blastic cells were positive for CD4, CD56 and CD43. All other T-cell, B-cell and myelomonocytic markers were negative. Flow cytometry immunophenotyping was performed in skin lesions from 2 patients and in blood and bone marrow from 2 affected patients which showed a CD4+CD56+CD123bright+HLA-DRbright+CD85kbright+ phenotype. Additional immunohistochemical studies were performed on biopsy specimens using CD68, CD99 and TdT markers as well the cell proliferation marker Ki67 and the results are shown in Table 1. All patients were treated with systemic chemotherapy except one who refused treatment and died 5 months after diagnosis. Six patients achieved complete remission (CR) and 1 had partial response (PR). Five initially responding patients relapsed after a median time of 10 monhts (9-30). One patient died in CR due to treatment toxicity. Relapsed patients received salvage chemotherapy regimens. Two patents are currently alive, one in CR and one with disease. Of note, patients with TdT+ tumors showed shorter median failure-free (11 vs. 19 months) and overall (13.5 vs. 20.5 months) survival as compared to patients with TdT- neoplasms. In summary, CD4/CD56 hematodermic tumors are clinically aggressive, highly proliferating neoplasms and conventional chemotherapy used often results in a complete response but quick relapses unresponsive to further treatment may be expected. The impact of TdT expression as a potential adverse prognostic factor should be explored in larger cohort of patients. The identification of definitive prognostic markers is mandatory for the selection of patients who can benefit from bone marrow transplantation.

Disclosures:
No relevant conflicts of interest to declare.