H a i r y C e l l L e u k e m i a
General
• HCL is a rare, low-grade, chronic lymphoproliferative disorder of B-cell origin.
• Primary manifestations are in blood, bone marrow, and spleen.
Clinical Features
• Usually older (40-60).
• Male: female = 5:1.
• Symptoms: splenomegaly but no lymphadenopathy.
Morphology
Blood
• "Hairy cells" (small lymphocytes with little cytoplasmic projections) present
– but not very many.
• Monocytopenia always present!
Bone marrow
• Hypercellular but loosely structured ("moth-eaten").
• Often with increased reticulin (making aspiration difficult).
Cytochemistry
• Hairy cells are TRAP (tartrate-resistant acid phosphatase) positive.
• Many other cells (neutrophils, monocytes, platelets) stain positively with acid
phosphatase, but the stain washes away when treated with tartrate.
Immunophenotype
• Positive for:
• B-cell antigens (CD19, CD20).
• CD25 (also on monocytes and T cells).
• CD11c (also on monocytes and T-cells).
• Negative for CD5 (the T-cell antigen expressed in CLL).
Laboratory Findings
• Pancytopenia (from marrow failure and sequestration of cells): anemia,
thrombocytopenia, and leukopenia.
• Even in cases where pancytopenia has not had time to develop, there is
always a monocytopenia! (Who knows why.)
Treatment and Prognosis
• Until recently, the only treatment for HCL was splenectomy and observation
(with a relatively grave prognosis).
• Now, using new chemotherapeutic treatments (pentostatin and 2-CDA),
patients can achieve complete remissions and live for many years.
