At a Glance

Hairy cell leukemia is an indolent neoplasm of mature B cells. The name is derived from the appearance of the cells, lymphoid cells with hair-like cytoplasmic projections, in the peripheral blood and bone marrow. Patients are usually middle-aged or older, frequently present with fatigue, weakness or fever, and are classically found to have splenomegaly and pancytopenia. The disease is more common in males than females (numerous studies have shown a male to female ratio of 5:1 or more). The disease usually involves the bone marrow and spleen. Patients usually do not have lymphadenopathy or extranodal masses.

What Tests Should I Request to Confirm My Clinical Dx? In addition, what follow-up tests might be useful?

A complete blood count (CBC) will often show pancytopenia, including a characteristic monocytopenia. There are usually very few circulating hairy cells. When a bone marrow examination is performed, typically, the marrow is reported as “inaspirable”, a “dry tap”, or difficult to aspirate. A bone marrow biopsy is usually diagnostic, showing a diffuse or patchy infiltrate with a “fried egg” appearance, cells with a moderate amount of cytoplasm neatly spaced one from another. Flow cytometry studies on the peripheral blood (if sufficient cells are present in the peripheral blood) and/or bone marrow demonstrate monoclonal B cells, which are negative for CD5 and CD10 and are positive for CD11c, CD25, and CD103 (the hairy cell-associated antigens).

Before the advent of acceptable flow cytometry, the diagnosis of hairy cell leukemia was based on cytochemical staining with the hairy cells showing positive staining for acid phosphatase in the presence of tartrate, tartrate-resistant acid phosphatase (TRAP) positivity.

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Are There Any Factors That Might Affect the Lab Results? In particular, does your patient take any medications – OTC drugs or Herbals – that might affect the lab results?

It is important to distinguish hairy cell leukemia from other B cell neoplasms, since treatment is different. Splenic lymphoma with villous lymphocytes (splenic marginal zone lymphoma) and hairy cell leukemia variant may be difficult to distinguish from hairy cell leukemia. It is important to correlate morphology, the flow cytometry immunophenotype, and clinical information about the patient. Harry cell leukemia is an indolent disease, and there are now several therapeutic options available. Patients may have discomfort from splenomegaly (spleens may become very large) and may develop significant neutropenia, making them susceptible to infection. Patients are usually followed for clinical symptomatology and with CBC to monitor peripheral blood counts.