Indolent B-Cell Lymphomas [C85.9]
Dipl.-Ing. (FH) Tanja Hinrichsen
Approximately 80-85% of all Non-Hodgkin lymphomas are B-cell neoplasms. The classification and nomenclature of B-cell neoplasms is based on their similarity to normal stages of the B-cell differentiation. The morphology and immunophenotype (see Immunobiology) suffice to diagnose most of the B-cell lymphomas. Since the majority of B-cell neoplams also exhibit characteristic genetic abnormalities, tumor cytogenetics can provide highly useful information for a differential diagnosis.
Chronic lymphocytic leukemia (see CLL)
The B-cell prolymphocytic leukemia (B-PLL) is a rare condition with unfavorable course. It frequently exhibits a complex karyotype, deletions in 17p13 in 50% of all cases and deletions of 13q14 in 27%.
Approximately 2% of all lymphoid neoplasms are splenic marginal zone lymphoma and exhibit a slow course of the disease. In approximately 40% of all cases there is a deletion 7q31-32. Other abnormalities affect the region 7q21 as well as partial trisomies of the long arm of chromosome 3.
Hairy cell leukemia (approximately 2% of all lymphoid neoplasms) (see hairy cell leukemia).
The MALT lymphoma (approximately 7-8% of all lymphoid neoplasms) has a slow course. Depending on the location of origin, mainly the translocations t(11;18)(q21;q21), t(1;14)(p22;q32), t(14;18)(q32;q21) and t(3;13)(p14.1;q32) are found.
Approximately 20% of all lymphoid neoplasms are follicular lymphomas. The course of the disease depends on the stage of the disease. Follicular lymphomas are characterized by the translocation t(14;18)(q32;q21) as well as BCL2 rearrangements. In most cases, the IGH/BCL2 fusion gene can also be detected by qualitative PCR. In addition, in 90% of all patients losses of 1p, 6q, 10q and 17p as well as gains of chromosomes 1, 6p, 7, 8, 12q, X and 18q/dup are detected. Abnormalities of 3q27 and/or BCL6 rearrangements are found in 5-15% of all cases, especially in grade 3B.
The mantle cell lymphoma (approx. 3-10% of all NHL cases) has been associated with a median survival time of 3-5 years. The translocation t(11;14)(q13;q32) with the CCND1/IGH fusion gene is present in nearly all cases and is considered a first event. In 40% of all cases, this fusion gene can be detected by qualitative PCR as well. Mantle cell lymphoma are characterized by a large number of secondary abnormalities: gains of 3q26, 7p21 and 8q24 and losses of 1p13-p31, 6q23-q27, 9p21, 11q22.3, 13q11-q13, 13q14-q24 and 17p13 as well as a trisomy of chromosome 12.
Diffuse large B-cell lymphoma (DLBCL) (approximately 25-30% of all NHL cases) show translocations with the region 3q27 in more than 30% of all cases. Translocations involving the BCL2 gene (18q21) are found in 20-30% of all cases. MYC rearrangements (8q24) have been associated with complex genetic abnormalities.