Fluorescence in situ hybridization (FISH) is a sensitive method for detecting small genomic alterations associated with a variety of hematological malignancies and solid tumors. FISH technology has several advantages over routine chromosomal analysis; such advantages include its ability to detect genomic abnormalities in non-viable and non-meristematic tissues, rapid turnaround times, and more Includes high resolution. However, FISH technology complements routine chromosome analysis and does not replace routine chromosome analysis for cancer diagnosis. B-cell lymphomas are a large heterogeneous group of diseases and include the majority of non-Hodgkin's lymphomas. The most common aberrations observed in these diseases are translocations or rearrangements of the IGH gene involving the 14q32 locus. This group includes follicular lymphoma (FL), Burkitt's lymphoma (BL), and diffuse large B-cell lymphoma (DLBCL). The characteristic chromosomal abnormality t(14;18) resulting in the IGH/BCL2 fusion is found in approximately 80% of FL and approximately 20-30% of DLBCL, whereas the majority of BL patients have the characteristic t (8; 14). BCL6 gene rearrangements have also been associated with B-cell lymphoma. Cyclin D1 gene rearrangements, particularly t(11;14), distinguish mantle cell lymphoma (ML) from other lymphoproliferative disorders and are diagnostic of ML. Although most of these abnormalities can be detected by routine chromosome analysis, interphase FISH analysis is sensitive enough to detect low-level clones and identify genetic abnormalities of prognostic and therapeutic importance. Fluorescence in situ hybridization (FISH) is a sensitive method for detecting small genomic alterations associated with a variety of hematological malignancies and solid tumors. FISH technology has several advantages over routine chromosomal analysis; such advantages include the ability of FISH technology to detect genomic abnormalities in non-viable and non-dividing tissues, rapid turnaround times, and more Includes high resolution. However, FISH technology complements routine chromosome analysis and does not replace routine chromosome analysis for cancer diagnosis. Fluorescence in situ hybridization (FISH) is a sensitive method for detecting small genomic alterations associated with a variety of hematological malignancies and solid tumors. FISH technology has several advantages over routine chromosomal analysis; such advantages include the ability of FISH technology to detect genomic abnormalities in non-viable and non-dividing tissues, rapid turnaround times, and more Includes high resolution. However, FISH technology complements routine chromosome analysis and does not replace routine chromosome analysis for cancer diagnosis. Fluorescence in situ hybridization (FISH) is a sensitive method for detecting small genomic alterations associated with a variety of hematological malignancies and solid tumors. FISH technology has several advantages over routine chromosomal analysis; such advantages include the ability of FISH technology to detect genomic abnormalities in non-viable and non-dividing tissues, rapid turnaround times, and more Includes high resolution. However, FISH technology complements routine chromosome analysis and does not replace routine chromosome analysis for cancer diagnosis. Chronic lymphocytic leukemia (CLL) is a small, mature B-cell leukemia that primarily affects adults over the age of 65. CLL is the most common lymphocytic malignancy, accounting for approximately 11% of all hematologic malignancies and 25% of all leukemias. Clonal cytogenetic abnormalities may be identified during routine chromosomal analysis in up to 50% of CLL patients. However, CLL clones (lymphocytes) do not divide in culture and are resistant to mitogens, making routine cytogenetic analysis difficult. FISH, on the other hand, is highly sensitive to detect genomic alterations that have a significant impact on the prognosis of CLL.