[556] Cutaneous Myeloid Dendritic Cell Malignancies

Shalini Verma, Constantin S Friedman, Wayne Tam, Cynthia M Magro. The University of Texas M.D. Anderson Cancer Center, Houston, TX; NYP-Weill Cornell Medical College, New York, NY

Background: Cutaneous dendritic cells neoplasms are exceedingly rare, and usually arise from plasmacytoid dendritic cells (pDCs). These neoplasms are categorized as blastic pDC neoplasms, also known as CD4+ CD56+ hematodermic malignancies. In contrast, myeloid dendritic cell (mDC) derived neoplasms represent a distinct type of hematodermic malignancy. The precedent literature regarding this entity is limited.
Design: Four cases of mDC malignancies were prospectively encountered in the routine and referral practices of one of the authors (CMM). The light microscopic studies were correlated with immunohistochemical results and clinical features.
Results: All patients were elderly ranging in age from 70 to 80 years of age (mean age 85 years); there were two males and two females. Each presented with a rapid onset skin rash. In each case the biopsies showed a noneffacing well differentiated small to intermediate sized monocytoid infiltrate with an unusual predilection to involve follicles, vessels, nerves, and the eccrine coil; there was accompanying attendant follicular mucinosis. The atypical monocytoid cells had a distinctive immunophenotype: they shared in common with the CD4+CD56+ hematodermic neoplasm positivity for CD4, CD56 and CD123. However at variance with the CD4+CD56+ hematodermic neoplasm was the expression amid the neoplastic cells for myeloid markers including CD68, CD11c, CD14 and lysozyme. In two cases there was peripheral blood chronic clonal monocytosis while in two patients the peripheral blood findings were more in keeping with acute myelogenous leukemia. Overall the findings were held to be consistent with a variably mature myeloid dendritic cell leukemia.
Conclusions: Cutaneous mDC neoplasms are clonal disorders of differentiated myeloid dendritic cells. The clinical settings are variable ranging from a chronic clonal monocytosis to one of acute myelogenous leukemia. Unlike the CD4+CD56+ hematodermic neoplasm, the clinical course ranges from a more indolent one, to an aggressive clinical course with death occurring shortly following the initial clinical presentation.
Category: Dermatopathology

Tuesday, March 20, 2012 9:30 AM

Poster Session III # 100, Tuesday Morning

 

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