Solitary cutaneous nodule of blastic plasmacytoid dendritic cell neoplasm progressing to overt leukemia cutis after chemotherapy: immunohistology and FISH analysis confirmed the diagnosis.

Blastic plasmacytoid dendritic cell (BPDC) neoplasm, formerly called blastic natural killer cell lymphoma or CD4+/CD56+ hematodermic neoplasm, is a rare tumor entity, now regarded to be derived from the plasmacytoid dendritic cell (PDC) lineage. Because over 90% of patients present with skin lesions usually early in their disease, dermatologists have to be familiar with the specific diagnostic features and the clinical course of this devastating disease. We present a woman with a long standing solitary skin tumor of BPDC neoplasm, who experienced a deleterious clinical course, which is typical for this disease. Phenotypic and karyotypic characteristics distinguishing this tumor from myelomonocytic leukemia with skin involvement are presented.