Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (343 page)

   
Peripheral blood smear (PBS)
is heavily populated by medium/large-sized “prolymphocytes,” with moderately condensed chromatin and a single, prominent, vesicular nucleolus. The prolymphocytes must exceed 55% of lymphocytes but are frequently >90%.

   
Bone marrow
is infiltrated in an interstitial pattern by prolymphocytes.

   
Lymph nodes
may show vague nodularity, but proliferation centers are absent.

   
Immunophenotype

   The prolymphocytes express bright surface IgM and IgD and bright CD20 (see Table
9-3
) as well as CD19, CD20, CD22, CD79a and b, and FMC7.

   Expression of CD5 and CD23 is weak or absent. CD25, CD11c, and CD103 are negative.

   ZAP 70 and CD38 are expressed in half the cases.

   
Cytogenetics
. There are few studies available. Cases with t(11;14)(13;q32) should be considered leukemic variants of mantle cell lymphoma. Similarly, abnormalities common in CLL including deletions in 6q 11q (ATM), 13q, and 17p (TP53) are considered evidence of progression, from CLL. Molecular studies of p53 detect mutations in more than half the cases.

Suggested Reading

Campo E, Catovsky D, Montserrat E, et al. B-cell prolymphocytic leukaemia. In:
WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues
, 4th ed. Lyon, France: International Agency for Research on Cancer; 2008:183–184.

HAIRY CELL LEUKEMIA

   Definition

Hairy cell leukemia (HCL) is a rare indolent B-cell lymphoproliferative neoplasm, characterized by the accumulation of small mature B lymphocytes with abundant cytoplasm and hairy projections. The disease has a 4:1 to 3:1 male-to-female ratio.

   Who Should Be Suspected?

Individuals who present with abdominal fullness due to splenomegaly and fatigue, weakness, and weight loss. Because of severe cytopenias, some patients may present with infections or excessive bleeding.

   Laboratory Findings

   
CBC
: