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Lymphoma - B cell neoplasms

B cell lymphoma subtypes

Precursor B cell lymphoblastic leukemia / lymphoblastic lymphoma


Reviewer: Nikhil Sangle, M.D., University of Utah and ARUP Laboratories (see Reviewers page)
Revised: 13 March 2011, last major update March 2011
Copyright: (c) 2001-2011, PathologyOutlines.com, Inc.


Terminology
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● Disorder of immature B cells that usually affects children, and often presents with diffuse multi-organ involvement

Description
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● Pre-B lymphoblastic leukemia is defined as 20% or more lymphoblasts in bone marrow

Etiology
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● Derived from pre-germinal center naive B cells with nonmutated Vh region genes

Clinical features
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● Usually children, presents with pancytopenia due to extensive marrow involvement, stormy onset of symptoms, bone pain due to marrow expansion, hepatosplenomegaly due to neoplastic infiltration, testicular involvement, CNS symptoms due to meningeal spread, frequent skin involvement
● 85% of acute lymphoblastic leukemias (ALL) are B cell, compared to 10-20% of lymphoblastic lymphomas (remainder are T cell)
● Aggressive, but 2/3 cured with chemotherapy
● Recommended to classify/manage B-ALL with mature phenotype, L1 morphology, and without c-myc translocations as pre-B lymphoblastic/lymphoma, not Burkitt lymphoma (Arch Pathol Lab Med 2003;127:1340)

Lymphoma cases:
● Median age 20 years, 88% age 35 years or less; 2/3 female, usually extranodal (cutaneous nodules, bone or nodal involvement, NO marrow or mediastinal involvement, Am J Surg Pathol 2000;24:1480)
● Usually stage 1 or 2
● Prognosis better than leukemia, but 28% died after median 5 years
● Often 21q alterations, resembles blastoid variant of mantle cell lymphoma
● Rarely develop leukemia

Prognostic factors
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Good prognostic factors: age 2-10 years, early pre-B phenotype, hyperploidy, t(12,21)
Poor prognostic factors (give bone marrow transplantation): under age 2 or teenager/young adult, t(9;22)

B lymphoblastic leukemia/lymphoma with recurrent genetic abnormalities:
Good prognosis - t(12;21)(p13;q22) TEL-AML1 (ETV6-RUNX1); blasts with hyperdiploidy (50–66 chromosomes with no structural alterations)
Poor prognosis - t(9;22)(q34;q11.2) BCR-ABL1; t(v;11q23) MLL rearranged; blasts with hypodiploidy (<46 chromosomes); t(1;19)(q23;p13.3) E2A-PBX1

Micro description
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● Intermediate sized blast-like cells with scant cytoplasm, round or convoluted nuclei, fine chromatin, indistinct nucleoli, frequent mitosis
● May have “starry sky” appearance (similar to Burkitt)
● Some lymphoblasts have cytoplasmic pseudopods (hand mirror cells); usually no sclerosis

Micro images
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TdT negative cases; B cell ALL L1

Various images

Positive stains
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● CD19 or CD20 or CD79a (Am J Clin Path 2001;115:868), TdT (only rarely negative, Arch Pathol Lab Med 2000;124:92)
● Also CD99, CD179a and CD179b (light chain substitutes in precursor B cells, Mod Pathol 2004;17:423)
● PAX5 and CD79a demonstrate B-lineage in tissues
● Variable CD10 (76%), CD20 (54%), CD22 and CD34, CD13 and CD33 (myeloid markers)

Negative stains
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● Surface immunoglobulin, cytoplasmic IgM, T cell antigens, CD15, CD30, CD45
Note: may resemble Ewing’s sarcoma and be CD99+, CD45-, CD20-, CD3-, weakly positive for vimentin (Am J Clin Path 2001;115:11)

Molecular
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● t(1;14)(q25;q32) - IHX4 and IgH
● t(1;19)(q23;p13): PBX1 and E2A (30%) - unfavorable
● t(5;14)(q31;q32) - IL3 and IgH
● t(4;11)(q21;q23): AF4 and MLL (10%) - unfavorable
● t(9;22)(q34;q11): bcr and c-abl [Philadelphia chromosome] (5-20%) - unfavorable
● t(12,21)(p13;q22): ETV6-CBFA2 (TEL and AML1) (20%) - favorable
● Most tumors are hyperdiploid (>50 chromosomes, favorable), some are pseudodiploid

Differential diagnosis (based on morphology)
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Ewing’s sarcoma: negative for CD43, CD79a, CD179a, CD179b, TdT and immunoglobulin or T cell receptor rearrangement, strong/diffuse for vimentin
AML: prominent nucleoli, delicate chromatin, fine azurophilic cytoplasmic granules, TdT negative, positive for myeloid markers (usually)
● Also Burkitt lymphoma, granulocytic sarcoma, Hodgkin lymphoma, mantle cell lymphoma-blastic variant

End of Lymphoma - B cell neoplasms > B cell lymphoma subtypes > Precursor B cell lymphoblastic leukemia / lymphoblastic lymphoma


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