Insights From: Gary J. Schiller, MD, UCLA David Geffen School of Medicine; Leslie Andritsos, MD, UNM Comprehensive Cancer Center
Gary J. Schiller, MD: Hairy cell leukemia [HCL] is still a mysterious disease. It’s an unusual, relatively indolent lymphoproliferative disease. And the toughest thing about hairy cell leukemia is thinking about hairy cell leukemia. So the diagnosis, although it easily can be made by analysis of either the peripheral blood or bone marrow, has to be considered in a patient with neutropenia. I think the biggest problem with hairy cell leukemia is just thinking of it. If you manage to think of it in the work-up of neutropenia, then there are a variety of mechanisms to make a diagnosis. But how it occurs and in what patient population, this still is relatively mysterious.
The characteristic patient is a middle-aged, generally Caucasian man. However, we’ve seen hairy cell leukemia in all types of different demographic groups. So there’s not one demographic profile that’s characteristic for hairy cell leukemia. Likewise, this being a chronic lymphoproliferative disorder, it typically is not associated with lymphocytosis. Again, it’s tricky. Where it comes from, whether it has a viral etiology, whether it’s induced by exposures, whether it is in some way genetically inherited—all of this is mysterious. And the incidence is sufficiently low and it’s hard to get some idea of a pattern that could give us insight into how it develops.
Leslie Andritsos, MD: In the past, patients with hairy cell leukemia tended to present with massive splenomegaly and pancytopenia. But in modern times where routine blood testing is performed on most patients, a lot of patients are diagnosed with mild cytopenia and usually don’t have massive splenomegaly as a presenting sign or symptom. Many patients do present with infections, however, because of the immunocompromise caused by the underlying disease. Hairy cell leukemia can be very difficult to diagnose because it is a rare disease and many providers are not thinking of that top of the mind. But once the bone marrow biopsy is obtained, it should be a pretty straightforward diagnosis.
Gary J. Schiller, MD: Prevalence of HCL is not clear because I think it’s underdiagnosed. The incidence is low. The disease is infrequently diagnosed, but patients live a long time. Those who have been successfully identified are generally successfully treated with response rates well over 85% or 90%. So the prevalence in the population should be fairly considerable because people live a long time. But the diagnosis is hard to make, and therefore the incidence is low, and we might be under detecting cases of hairy cell leukemia.