Localized skin‐limited blastic plasmacytoid dendritic cell neoplasm

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A 32-year-old man presented with a 7-month history of progressive painless, nonpruritic skin and soft tissue lesion on his left leg. He had no systemic or B symptoms. The physical examination showed a violaceus lesion soft in consistency on the left leg (Figures 1 and 2). MRI showed an oval lesion with hypointensity signal in T1 and hyperintensity in T2, with homogeneous enhance postcontrast study, and diffusion-restriction. There was no palpable lymphadenopathy or hepatosplenomegaly. The skin lesion was biopsied and showed atypical cells (Figure 3). Immunohistochemical analysis showed cells that were positive for CD4, CD56, CD123, SPIB, TdT, and negative for MNDA (Figure 4), which supported the diagnosis of blastic plasmacytoid dendritic-cell neoplasm (BPDCN). Complete blood count was unremarkable and peripheral blood smear did not show immature cells. Bone marrow aspirate/biopsy did not reveal the presence of neoplastic plasmacytoid dendritic cells. An 18(F)–FDG-PET-CT imaging did not reveal evidence of other lesions (Figure 5). The next-generation sequencing (NGS) of the skin lesion biopsy specimen revealed NRAS mutation. NGS of the bone marrow biopsy specimen showed no pathogenic mutations. BPDCN is a rare, but aggressive, hematologic malignancy. The clinical features and evolution consist of two main patterns: (A) Indolent onset dominate by skin lesions followed by tumor dissemination (70–90%) and (B) Acute leukemia features with systemic involvement from the beginning (10-30%) [1, 2]. Skin lesions can be extremely heterogeneous, but more often they are multiple and can involve any body site [2]. Typically affect older men and precede dissemination extracutaneous by a few months [1]. Confirmation of a diagnosis can pose a significant challenge in many cases, and therefore, the clinician and pathologist must have a high degree of suspicion, particularly in patients presenting with skin lesions and cytopenias. Although lack of systemic involvement at presentation may seem reassuring, survival is poor regardless of presentation [1, 2]. This work was supported by grants from the Instituto de Salud Carlos III (ISCIII) of the Spanish Ministry of Economy and Competence (MINECO, FEDER, RTICC ISCIII, and Centro de Investigación Biomédica en Red Cáncer - CIBERONC) (SAF2013-47416-R, RD06/0020/0107-RD012/0036/0060, and Plan Nacional I+D+I: PIE15/0081, PI16/01294, PI17/2172, PI17/00272 and PI19/00715), GILEAD (GL18/00019), Asociación Española Contra el Cáncer (AECC; PROYE18054PIRI), and the Madrid Autonomous Community. The authors report no conflict of interest. All authors wrote and edited the manuscript. The patient provided written informed consent for the publication of this Clinical Picture.

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