Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (365 page)

   
CBC
: A leukemic, ALL-like phase can be seen in patients with bulky disease (Burkitt leukemia variant).

   
Immunophenotype
: BL has a mature B-cell phenotype. The cells have monotypic surface IgM and are positive for CD10, CD19, CD20, CD22, CD38, CD43, and CD79a. CD5 and TdT are negative. Bcl-2 is typically absent. Proliferation fraction by Ki-67 is nearly 100%.

   
Cytogenetics
: Translocation
(8;14) (q24;q32)
is found in 80% of cases; in the rest,
t(8;22)(q24;q11)
or
t(2;8)(p11;q24).
These translocations are readily detected by metaphase analysis. FISH analysis may also be used but can miss some rearrangements because the break points are widely heterogeneous.

   
Genetic studies
: C-MYC dysregulation with BCL-6
⁺
has long been associated with BL. The MYC translocation is considered a primary event. However, deregulation of MYC has been shown to occur in other B-cell lymphomas, most often as a secondary event, the so-called “double-hit,” indicating an aggressive course. Gene profile studies help differentiate atypical BL from diffuse large cell lymphoma, but no uniform criteria have yet been established.

Suggested Readings

Jaffe ES, Pittaluga S. Aggressive B-Cell lymphomas: a review of new and old entities in the WHO classification.
Hematology Am Soc Hematol Educ Program.
2011;2011:506–514.

Piccaluga PP, De Falco G, Kustagi M, et al. Gene expression analysis uncovers similarity and differences among Burkitt lymphoma subtypes.
Blood.
2011;117:3596–3608.

CUTANEOUS T-CELL LYMPHOMAS: MYCOSIS FUNGOIDES (MF) AND SÉZARY SYNDROME (SS)

   Definition

Cutaneous T-cell lymphomas (CTCL) are a heterogeneous group of T-cell lymphomas. MF and SS are tumors of the CD4
⁺
helper T cells. MF is the more common; it is an indolent, extranodal non-Hodgkin lymphoma. SS is a leukemic variant in which typical malignant Sézary cells circulate in the peripheral blood; they can also be found in skin and lymph nodes.

   Who Should Be Suspected?

An elderly patient with persistent and progressive pruritic patches, plaques, or subcutaneous tumors (MF). An elderly patient with a high number of atypical (cerebriform) T-cell lymphocytes in the peripheral blood; erythroderma and extracutaneous infiltrates, with marked lymphadenopathy (SS).

   Laboratory Findings

Diagnosis is established by the typical morphology of skin biopsy for MF and SS, as well as by the study of peripheral blood for SS.

   
Bone marrow and liver biopsies
are usually normal.

   
CBC
is normal in MF. Total WBC count is often increased in SS. More than 1,000/μL cells are atypical, easily identifiable lymphocytes.

   
Skin biopsy
in MF demonstrates atypical mononuclear cells with cerebriform nuclei, infiltrating the upper dermis.

   
ESR, Hb, and platelet counts
are usually normal in both conditions.