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B-cell lymphoblastic lymphoma

Wednesday 18 January 2006

B lymphoblastic leukemia; B-cell lymphoblastic leukaemia; precursor B lymphoblastic lymphoma

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See also : lymphoblastic lymphoma

Definition : B-cell lymphoblastic lymphoma represents approximately 15% of all cases of lymphoblastic lymphoma. B-cell lymphoblastic lymphoma is most common in older children and young adults.

Patients with this type of lymphoma present with rapidly enlarging lymph nodes or soft tissue masses.

In contrast to T-cell lymphoblastic lymphoma, the B-lymphoblastic lymphoma rarely involves the mediastinum.

The distinction between B-cell lymphoblastic lymphoma and precursor B-cell acute lymphoblastic leukemia is made through examination of the bone marrow biopsy specimen.

In cases in which fewer than 25% of the marrow cells are blasts, a diagnosis of B-cell lymphoblastic lymphoma should be made.

One feature typical of lymphoblastic lymphoma (B or T) is infiltration through perinodal fat and linear infiltrates in the capsular collagen.

The nodal architecture is effaced by a diffuse proliferation of small and intermediate cells (12 to 14 mm) with fine or speckled chromatin, small or indistinct nucleoli, and scant cytoplasm.

The mitotic rate is frequently elevated, and necrosis may be present.

Immunochemistry

A CD45 (dim to negative), terminal deoxynucleotidyl transferase (TdT) positive, CD19+, CD20−, sIg− phenotype sets these tumors apart from lymphomas composed of mature (nonblastoid) B-cells, including Burkitt lymphoma.

Almost all cases are positive for CD10 (common acute lymphocytic leukemia antigen or CALLA).

Localization

- nodal B-cell lymphoblastic lymphoma
- extranodal B lymphoblastic lymphoma

Immunophenotype

+ TdT CD19 CD79a
- CD3
+/- CD10 CD24 CD20 CD22 CD45 CD13 CD33

Differential diagnosis

Important in the differential diagnosis in children are other small blue cell tumors including granulocytic sarcoma/chloroma, Ewing sarcoma/primitive neuroectodermal tumor, embryonal rhabdomyosarcoma that can be distinguished by phenotype, although care should be taken not to overvalue results from any single stain.

For example, like Ewing sarcoma, lymphoblastic lymphomas are often CD45− and CD99+.

Cytogenetics

- t(9;22)(q34;q11) (BCR/ABL) (BCR at 9q34 and ABL at 22q11)
- t(v;11))v;q23) (v/MLL) (MLL rearrangement at 11q23) (CD10-, CD24-, CD15+)
- t(12;21)(p13;q22) (ETV6/RUNX1 or TEL/AML1) (ETV6 at 12p13 and RUNX1 at 21q22) (cd10+, CD34-, CD20-)
- t(1;19)(q23;p13) (PBX1/TCF3 or PBX/E2A) (PBX1 at 1q23 and TCF3 at 19p13) (CD10+, CD34-, CD20-, mu +)
- hypodiploid
- hyperdiploid >50

- deletions

  • del(6q)
  • del(9p)
  • del(12p)

- hyperdiploid @<@51
- near tumoral triploidy
- near tumoral tetraploidy

See also

- Lymphomas

  • lymphoblastic lymphomas
    • T-cell lymphoblastic lymphoma

- B-cell acute lymphoblastic leukemia (ALL)