Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (370 page)

MALT Lymphoma

For patients presenting with gastric MALT lymphoma, the diagnosis is established by endoscopic biopsy.

   
Microbiology
: Studies for
H. pylori
are positive for gastric MALT lymphoma, but other microbes, as well as chronic stimulation due to autoimmune diseases, have been implicated in pathogenesis.

   
Immunophenotype
: The tumor cells express B-cell–associated antigens: CD19, CD20, CD22, CD79a, and complement receptors CD21 and CD35. They are negative for CD5, CD10, and CD23. This immunophenotype is helpful in the differential diagnosis of other lymphomas.

   
Cytogenetics
: Four recurrent chromosomal translocations have been described: t(11;18) (q21;q21) BIRC3-MALT1; t(14;18)(q32;q21) IGHMALT1; and less commonly, t(1;14)(p22;q32) BCL10-IGH; and t(3;14) (p13;q32) FOXP-IGH. Trisomy 3 is present in 60% of cases.

   
Immunohistochemistry
: Nuclear expression of BCL-10 or NF-kappa B is associated with resistance to antibiotic therapy.

Suggested Reading

Zinzani PL. The many faces of marginal zone lymphoma.
Hematology Am Soc Hematol Educ Program.
2012;2012:426–432.

POSTTRANSPLANT LYMPHOPROLIFERATIVE DISORDER (PTLD)

   Definition

Lymphoma is the most common malignancy following stem cell or solid organ transplantation. PTLD comprises a spectrum of lymphomas classified by the WHO as early lesions, polymorphic PTLD, monomorphic PTLD (classified according to B-/T-cell lymphomas they resemble), and classic Hodgkin lymphoma-like PTLD. More than 90% of early cases (<1 year after transplantation) are EBV positive. Later cases (>2 years posttransplantation) are less often associated with EBV positivity, and their etiology is uncertain.

   Who Should Be Suspected?

Posttransplant patients who present with fever, generalized lymphadenopathy, hepatosplenomegaly not due to a documented infection. The GI tract, lungs, and liver may also be involved, occasionally as initial localizations. The incidence of PTLD correlates with the intensity of immunosuppression. It is seen sometimes following unrelated donor allogeneic stem cell transplantation or umbilical cord blood transplants after intensive immunosuppression.

   Laboratory Findings

   Peripheral blood may show very atypical plasmacytic lymphocytes.

   Lymph node biopsy or fine needle aspiration is essential for diagnosis and classification. It reveals atypical plasmacytoid lymphoid cells.

   Bone marrow biopsy should be done if no other tissue source is readily obtained.

   Flow cytometry of lymph nodes or bone marrow biopsy reveals κ/λ ratio of 5:1.

   EBV clonality and load help define the etiology.