Blastic plasmacytoid dendritic cell neoplasm with cutaneous manifestation, report of a rare case and literature review.

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare, clinically aggressive tumour derived from the precursors of plasmacytoid dendritic cells with a high frequency of cutaneous and bone marrow involvement and leukemic dissemination. This entity is a diagnostic challenge due to its morphological overlap with cutaneous lymphoma or secondary cutaneous involvement by myeloid leukemia. We report a 71-year-old man who initially presented with scalp lesions, extending to chest and back with rapid increase in size and number. These lesions were mildly pruritic but non-painful and there was no history of previous similar skin rashes. He was otherwise asymptomatic. An initial skin biopsy was reported as atypical lymphocytic infiltrate suspicious for lymphoproliferative disorder. Histopathology of a second skin punch biopsy specimen and immunohistochemistry at our institution demonstrated that the tumour cells were intermediate-sized with irregularly shaped nuclei with fine, immature chromatin and blastoid morphology. Based on a large immunohistochemical panel, cells were positive for CD4, CD43, CD2, CD56, CD33, TdT and CD123 and negative for CD20, CD3, CD5, PAX5, CD138, CD34, CD68, CD30, CD117, EBER-ISH, TIA-1, lysozyme and myeloperoxidase. The patient was subsequently treated with hyper-CVAD (cyclophosphamide, vincristine, doxorubicin, and dexamethasone followed by intrathecal methotrexate and cytarabine) chemotherapy and is currently in remission. This diagnosis is rendered difficult owing to common morphological overlaps and rarity of this malignancy. These neoplasms are highly aggressive, therefore; strong suspicion and detection will help in early therapeutic interventions and may have a significant impact on patient's survival. [ABSTRACT FROM AUTHOR]