Cytomorphological features of blastic plasmacytoid dendritic cell neoplasm on FNA and cerebrospinal fluid cytology: A review of 6 cases

BACKGROUND Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare hematopoietic tumor that was once believed to be derived from natural killer cells and is now recognized as originating from precursors of plasmacytoid dendritic cells. It generally involves the skin and has an aggressive clinical course. Due to its highly malignant behavior, a fast and accurate diagnosis of this condition is of the utmost importance. METHODS Six cytology specimens from 5 patients diagnosed with BPDCN were reviewed as well as their clinical records. Findings were compared with 3 previously published cases. RESULTS Two exfoliative cytology specimens (cerebrospinal fluid) and 4 fine‐needle aspiration specimens (3 lymph node specimens and 1 cutaneous specimen) were reviewed. The cytomorphological aspects were similar in all cases. The smears were hypercellular with a monotonous population of intermediate‐sized cells, dispersed singly or arranged in loose aggregates. The cells had round to oval nuclei, with fine chromatin and prominent nucleoli; the cytoplasm was generally scant, without visible granules. Intracytoplasmic microvacuoles were found in the majority of cases. Four cases were also characterized by flow cytometry, which revealed expression of CD 123, CD56 and/or CD4. Fine‐needle aspiration was used in 1 case for primary diagnosis. Histological confirmation was available in all cases. CONCLUSIONS BPDCN is a highly malignant neoplasm with a poor outcome. Cytology, in association with flow cytometry immunophenotyping and clinical history, is a reliable method with which to establish the diagnosis. Cancer Cytopathol 2016;124:196–202. © 2015 American Cancer Society. Blastic plasmacytoid dendritic cell neoplasm is a recently described entity with a specific phenotype and poor outcome. Cytology, in association with flow cytometry, is a reliable method with which to establish the diagnosis.