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Genetic lesions that are exclusively seen in cases of T-cell lineage leukemias are shaded in gray. All other genetic subtypes are either exclusively or primarily seen in cases of B-cell lineage ALL.

Genetic lesions that are exclusively seen in cases of T-cell lineage leukemias are shaded in gray. All other genetic subtypes are either exclusively or primarily seen in cases of B-cell lineage ALL.

Adapted from data presented in Pui CH, Relling MV, Downing JR: Acute lymphoblastic leukemia. N Engl J Med 350:1535-1548, 2004.

node enlargement and a high growth fraction, in contrast to its African variant, which is associated with EBV and usually presents in a more indolent manner, often as a jaw mass (lumpy jaw), and responds to more modest treatment.51 The non-African variant is treated with hyperfractionated alkylating agents and cycle-active treatment rather than with conventional ALL protocols, which produce inferior results.23 52 Several unique chromosome translocations include the typical t(8;14) involving the immunoglobulin gene IgH (on chromosome 14, a site frequently involved with a variety of malignant lymphomas and leukemias of lymphoid origin) and the c-myc proto-oncogene. Less usual variant translocations t(2;8) and t(8;12) are also seen in morphologically typical Burkitt-type leukemia.53

Demonstration of these abnormalities may not be readily apparent by conventional cytogenetics, FISH or even RT-PCR may be required to identify the exact chromosome abnormality and establish cellular origin when morphology suggests Burkitt leukemia or another abnormality, but is not demonstrated by initial chromosome analysis.6-10

Table 10.2 Proposed WHO classification of lymphoid neoplasms

B-cell neoplasms Precursor B-cell neoplasm Precursor B-lymphoblastic leukemia/lymphoma (precursor B-cell acute lymphoblastic leukemia)

Mature (peripheral) B-cell neoplasmsa B-cell chronic lymphocytic leukemia/small lymphocytic lymphoma

B-cell prolymphocyte leukemia

Lymphoplasmacytic lymphoma

Splenic marginal zone B-cell lymphoma (+/— villous lymphocytes)

Hairy cell leukemia

Plasma cell myeloma/plasmacytoma

Extranodal marginal zone B-cell lymphoma of MALT type

Nodal marginal zone B-cell lymphoma (+/— monocy-

toid B cells)

Follicular lymphoma

Mantle-cell lymphoma

Diffuse large B-cell lymphoma

Mediastinal large B-cell lymphoma

Primary effusion lymphoma

Burkitt lymphoma/Burkitt-cell leukemia

T-cell and NK-cell neoplasms Precursor T-cell neoplasm Precursor T-lymphoblastic lymphoma/leukemia (precursor T-cell ALL)

Mature (peripheral) T-cell neoplasms3 T-cell prolymphocyte leukemia T-cell granular lymphocytic leukemia Aggressive NK-cell leukemia Adult T-cell lymphoma/leukemia (HTLV1+) Extranodal NK/T-cell lymphoma, nasal type Enteropathy-type T-cell lymphoma Hepatosplenic gamma-delta T-cell lymphoma Subcutaneous panniculitis-like T-cell lymphoma Mycosis fungoides/Sezary syndrome Anaplastic large-cell lymphoma, T/null cell, primary cutaneous type

Peripheral T-cell lymphoma, not otherwise characterized Angioimmunoblastic T-cell lymphoma Anaplastic large-cell lymphoma, T/null cell, primary systemic type

HTLV1+, human T-cell leukemia virus; MALT, mucosa-associ-ated lymphoid tissue; NK, natural killer. aB- and T-/NK-cell neoplasms are grouped according to major clinical presentations (predominantly disseminated/leukemic, primary extranodal, and predominantly nodal).

Adapted from Harris NL, Jaffe ES, Diebold J, et al.: World Health Organization classification of neoplastic diseases of the hematopoietic and lymphoid tissues: report of the Clinical Advisory Committee Meeting-Airlie House, Virginia, November 1997. J Clin Oncol 17:3835-3849, 1999.

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