in about 80% of cases.
Courtesy Dr. Brittney K. DeClerck
Imaging from a case of BPDCN revealed infiltrate of immature, blastoid cells showing cytologic atypia present throughout the dermis.
“You won’t see blastic plasmacytoid dendritic cell neoplasm listed on our primary cutaneous lymphoma classifications because it’s not technically a primary cutaneous disease,” Brittney K. DeClerck, MD, said during the annual meeting of the Pacific Dermatologic Association. “It’s a systemic disease that has secondary cutaneous manifestations. That’s a very important distinction to make, in terms of not missing the underlying disease associated with what might be commonly first seen on the skin.”
Dr. Brittney K. DeClerck
BPDCN is a malignancy of plasmacytoid dendritic cells, which capture, process, and present antigen, and allow the remainder of the immune system to be activated. “They are mainly derived from the myeloid cell lineage, and possibly from the lymphoid line in a subset of cases,” said Dr. DeClerck, associate professor of clinical pathology and dermatology at the University of Southern California, Los Angeles. “They secrete high levels of type I interferons, which is important for antiviral immunity, but they can also be implicated in severe systemic inflammatory diseases, such as systemic lupus erythematosus and systemic sclerosis.”
BPDCN involves the skin in about 80% of cases, she added, “but invariably at some point it involves the bone marrow and has an acute leukemic presentation, whether or not it happens concurrently with what we see on the skin as dermatologists. We also see variable involvement of the peripheral blood, lymph nodes, and the central nervous system.”
The classification of BPDCN has changed over time based on evolving immunohistochemical markers and technologies. For example, in 1995 it was called agranular CD4+ NK cell leukemia, in 2001 it was called blastic NK-cell lymphoma, in 2005 it was called CD4+/CD56+ hematodermic neoplasm, and in 2008 it was called BPDCN (AML subset). In 2016 it became classified as its own entity: BPDCN.
Because of changing nomenclature, the true incidence of the disease is unknown, but according to the best available literature, 75% of cases occur in men and the median age is between 60 and 70 years, “but all ages can be affected,” Dr. DeClerck said. “Cases seem to come in clusters. Our most recent cluster has been in our pediatric population. At Children’s Hospital Los Angeles, we’ve had three cases in the last couple of years. To me, that was a bit unusual.”
She added that 10%-20% of patients will have either a history of, or will develop another, hematologic malignancy, such as myelodysplastic syndrome (MDS), chronic myelogenous leukemia (CML), or acute myelogenous leukemia (AML).
The general prognosis of BPDCN is poor, and the mean time from onset of lesions to an actual diagnosis is about 6.2 months, which underscores the importance of early diagnosis, Dr. DeClerck said. “There can be some nondescript solitary lesions that patients can present with, so don’t hesitate to biopsy.” The median overall survival is less than 20 months, but patients under 60 years of age have a slightly better prognosis.