Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare type of blood and bone marrow cancer. It almost always affects the skin. BPDCN may also affect the bone marrow, lymph nodes, and/or central nervous system.  BPDCN was previously known as blastic natural killer (NK) cell lymphoma or CD4+/CD56+hematodermic neoplasm. 

BPDCN is a rare and aggressive disease. It newly affects approximately 500 to 1000 people in the United States each year. A disease is considered rare if it affects fewer than 200,000 people. 

Because it can be harder to research rare diseases, they can be challenging to understand, diagnose, treat, and cure.