Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare and aggressive hematologic malignancy of myeloid origin, primarily affecting elderly adults. It is characterized by immature-appearing cells and frequent skin involvement. Its occurrence in pediatric patients is exceptionally rare, often leading to diagnostic challenges due to its clinical and morphological overlap with acute leukemia.

We report the case of an 11-year-old male referred for evaluation of acute leukemia due to pancytopenia, circulating blasts, and facial skin lesions. Complete blood count revealed hemoglobin 8.6 g/dL, leukocytes 3,100/mm³, platelets 41,000/mm³, and 445 circulating blasts/mm³. Morphologic analysis of peripheral blood smears stained with May-Grünwald-Giemsa showed medium-sized immature cells with moderately to highly increased nuclear-cytoplasmic ratio, loose chromatin, prominent nucleoli, slightly basophilic agranular cytoplasm, and occasional pseudopods. Bone marrow flow cytometry identified a population with moderate CD45 expression and low-to-intermediate complexity, showing strong positivity for CD4, CD33, CD38, CD56, CD123, and HLA-DR, along with weak CD7 expression. B and T lineage markers were not significantly expressed. Cytogenetic analysis revealed a t(6;8)(p21.1;q24.2) translocation in all 20 metaphases examined. The immunophenotype was consistent with the classical BPDCN profile (CD4+, CD56+, CD123+, HLA-DR+, CD33+), as described in the literature (Garnache-Ottou et al., 2009; Pagano et al., 2016). The presence of the t(6;8)(p21.1;q24.2) translocation, not commonly reported in BPDCN, raises the possibility of an alternative oncogenic mechanism, particularly in the pediatric setting. Although chromosomal aberrations involving 8q24 (MYC locus) have been associated with aggressive hematologic malignancies, the clinical significance of this specific rearrangement remains unclear.

This case highlights the importance of integrating morphology, immunophenotyping, and cytogenetic analysis to accurately diagnose BPDCN, especially in atypical age groups. Early recognition is critical due to the disease's aggressive nature and potential therapeutic implications.