The Principles of Clinical Cytogenetics - Extra Materials - Springer

Cytogenetics of Hematologic Neoplasms 401
Other genetic lesions in BL include inactivation of TP53 secondary to mutation in up to 30% of
sporadic and endemic cases. It should be noted that MYC translocations are not entirely specific for
BL. For example, a MYC translocation has been reported in secondary precursor B-lymphoblastic
leukemia/lymphoma following follicular lymphoma.
Three clinical variants of BL are recognized, each manifesting its differences in clinical presentation,
morphology, and biology. The clinical presentation varies according to the epidemiology, subtype,
and site of involvement:
• Endemic Burkitt lymphoma. This lymphoma occurs in equatorial Africa, representing the most
common malignancy of childhood in this area, with an incidence peak at 4–7 years and a male to
female ratio of 2 : 1. Epstein-Barr virus (EBV) plays an important role in endemic BL.
• Sporadic Burkitt lymphoma. This variant is seen throughout the world, mainly in children and
young adults. The incidence is low, representing 1–2% of all lymphoma in western Europe and the
United States.
• Immunodeficiency-associated Burkitt lymphoma. This variant is seen primarily in association with
human immunodeficiency virus (HIV) infection, occurring often as the initial manifestation of
acquired immunodeficiency syndrome. Most patients present with advanced disease, often with a
high tumor burden because of the short doubling time of the tumor.
In endemic cases, the breakpoints on chromosome 14 involve the heavy-chain gene adjoining
region, whereas in sporadic cases, the translocation involves the Ig switch region.
The classical morphology of BL is observed in the endemic type and seen in a high percentage of
sporadic BL cases, particularly in children. The medium-sized cells show a diffuse, monotonous
pattern of infiltration.
The endemic and sporadic BLs are highly aggressive, but potentially curable. The treatment should
begin as early as possible because of short doubling time of the tumor. The outcome for childhood
Burkitt and Burkitt-like lymphomas has recently improved with the use of short and intensive B-cell
non-Hodgkin’s lymphoma-directed therapy (194).
Variants of BL include Burkitt lymphoma with plasmacytoid differentiation and atypical Burkitt/
Burkitt-like lymphoma.
MATURE T-CELL AND NK-CELL NEOPLASMS
Mature T-cell and natural killer (NK) cell neoplasms are relatively uncommon, but show a significant
difference in incidence throughout different parts of the world. For example, they are more
common in Asians than in other races (107). Association of Epstein–Barr virus with NK-/T-cell
lymphomas and NK-cell leukemias is well known. Clinically, these are among the most aggressive of
all hematopoietic and lymphoid neoplasms. They usually present at an advanced stage of clinical
course and are in general resistant to chemotherapy. The WHO definition of T- and NK-cell neoplasms
is based on morphological, immunophenotypic, and genetics features. The WHO histological
classification of mature T-cell and NK-cell neoplasms includes the following:
• Leukemic/disseminated type
T-Cell prolymphocytic leukemia
T-Cell large granular lymphocytic leukemia
Aggressive NK-cell leukemia
Adult T-cell leukemia lymphoma
• Cutaneous type
Blastic N cell lymphoma
Mycosis fungoides/Sézary syndrome
Primary cutaneous anaplastic lymphoma
Lymphoid papulosis