Shared insight on methods to identify blastic plasmacytoid dendritic cell neoplasm followed by updated classifications from the World Health Organization.
Naveen Pemmaraju, MD: As you make those comments, on the next slide is exactly what you’re talking about. BPDCN [blastic plasmacytoid dendritic cell neoplasm] is a visual disease. Most of us as hematologists have not worked with dermatologists closely in our training, and this is essential as you mentioned. Here are some examples of cases throughout the world of patients with these skin lesions that you mentioned. Sometimes they’re large and painful; sometimes they’re subtle and the patient may not even notice it, the loved one notices it. Dr McCloskey, for you and me as hematologists in the clinic, how commonly do you work with dermatologists, and can you think of other examples of where you would see skin lesions in patients with leukemia?
James McCloskey, MD: That’s a great question, and I think what we’re getting at here is that there remains an important relationship between the pathologist and oncologist. As we look at how practices are shifting over time, oftentimes outsourcing a lot of our laboratory testing, it’s important to remember that a conversation with the pathologist still is often crucial in terms of providing them details about what’s going on clinically to help guide the process of arriving at the right diagnosis. I think that in our experience we’ve had patients who present to us with the most benign looking lesions, to lesions that look scary like some of these you see here. As an acute leukemia physician, it’s important to understand that most of the lesions I biopsy are probably not going to be BPDCN. But there’s still valuable information that we obtain from thoroughly evaluating the extent of a patient’s disease, even if they have AML [acute myeloid leukemia] and this ends up being leukemia cutis, which is far and away the most common lesion that we see. You mentioned that patients might have other hematologic malignancies, other myeloid diseases, so it’s still important we check to see if these lesions might be myeloid sarcoma. For some of our patients who might be neutropenic for long periods of times, there might even be a fungal infection or something else in the skin, where we need to look for the other lymphoproliferative diseases that can involve the skin. By thoroughly investigating whatever is happening from a cutaneous standpoint, it often helps us to arrive at the right diagnosis.
Naveen Pemmaraju, MD: Great discussion, and again as both you and Dr Gru nicely mentioned, this slide puts it all into perspective. You’re trying to think about common and rare diseases. You’re trying to put together a diagnosis, and then the name and the classification has changed as shown here. Dr Gru nicely mentioned these. I think what we want to tell our audience is that hot off the press, 2022, the fifth edition of WHO [World Health Organization Classification of Haematolymphoid Tumours: Myeloid/Histiocytic/Dendric Neoplasms], which many of us have been a part of, is now reclassifying BPDCN. It’s keeping the name but distinguishing an immature and a mature form. It’s still BPDCN, the disease that we know, but now placing it under the myeloid, histiocytic, dendritic cell neoplasms. Again, furthering evolution and understanding biological underpinning of a disease.
Overall we all believe this is a net positive for our field as we learn more. As we dive deeper into the fifth edition WHO, one thing that’s cool to see for us is under this PDC neoplasm, plasmacytoid dendritic cell neoplasm, in addition to BPDCN, there is this mature plasmacytoid dendritic cell proliferation associated with myeloid neoplasms. Maybe that is a CMML [chronic myelomonocytic leukemia] that can be diagnosed with a PDC. Again, letting people know you can see PDC proliferations, but it’s not always BPDCN. I think this is a very important point both of you raised.
Transcript edited for clarity.