Blastic plasmacytoid dendritic cell neoplasm with aberrant cytoplasmic CD3 expression

A 47-year-old man was admitted to Ruijin Hospital (Shanghai, China) in July, 2025, with widespread, tender, and violaceous cutaneous nodules on his trunk and extremities. PET–CT revealed hypermetabolic activity in the skin lesions, which involved cervical and inguinal lymph nodes (maximum standardised uptake value of 3·6–7·1). Laboratory studies revealed a white blood cell count of 11 × 109 cells per L. A skin biopsy showed a diffuse dermal infiltrate of monomorphic blastoid cells. Immunohistochemical analysis revealed that the neoplastic cells expressed CD123, TCF4, TCL1, CD4, CD56, HLA-DR, and aberrant cytoplasmic CD3 (figure A), with partial expression of CD2 and CD7.