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CBFB t(16;16), inv(16) by FISH

Test Code

F CBFB

Test Synonyms

inv(16)

Associations

Acute myelogenous leukemia (AML), Eosinophilia M4eo

Methodology

Fluorescence in situ Hybridization (FISH)

Turnaround Time

3-5 days

Specimen Requirements

2.0 mL (min. 1.0 mL) peripheral blood in sodium heparin preferred, EDTA accepted
1.0 mL (min. 0.5 mL) bone marrow in sodium heparin preferred, EDTA accepted
5 mm^3 fresh tissue or 3.0 mL (min. 2.0 mL) FNA in MPLN RPMI media

Specimen Stability
Peripheral blood and bone marrow stable at 18-25°C for 72 hours
Fresh tissue or FNA at 2-8°C stable for 72 hours
Storage & Handling

Whole blood and bone marrow, ship ambient
Fresh tissue and FNA ship in a Styrofoam container with a cool/refrigerated pack (Do not allow cool pack to directly contact sample)

Causes for Rejection

Clotted specimen; Specimen exposed to extreme temperature; Anticoagulant toxic to cells; Insufficient number of cells

Reference Range

In a normal nucleus, two fused red/green (yellow) signals are observed. The pattern in a nucleus containing an inv(16) results in separate red and green signals appearing on opposite arms of the inverted 16 chromosome. The pattern of t(16;16)(p13;q22) results in a fused red/green signal on the q arm of one of the 16 chromosomes and a green signal on the other arm of 16, while the 16 chromosome homolog will only contain the red signal on one arm.

Description

Structural abnormalities of chromosome 16 involving the CBFB locus have been identified in a specific group of patients with acute myelomonocytic leukemia (AML) type M4 with marked eosinophilia. Inversion 16, translocation 16;16, and deletion 16q with breakpoints within the CBFB gene are considered variants of each other, which share common clinical features including a favorable prognosis when compared to the standard risk for AML patients.

Deletions of the proximal region of the MYH11 gene located at 16p13.1 have been detected in about 20% of patients with inv(16). The identification of inv(16)/t(16;16) can be difficult by conventional cytogenetics, especially on suboptimal G-banded chromosomes and in cases with a masked inv(16) by translocations. The inv(16) has been shown to fuse the CBFB gene on 16q22 with the MYH11 gene on 16p13 giving rise to a chimeric protein. FISH can detect this rearrangement in either interphase or metaphase cells.

References
  1. Egan N et al. (2004). Deletions of CBFB in a patient with acute myelomonocytic leukemia (AML M4Eo) and inversion 16. Cancer Genet Cytogenet 154(1):60.
  2. Aventin A et al. (2002). Chromosome 16 inversion-associated translocations in acute myeloid leukemia elucidated using a dual-color CBFB DNA probe. Cancer Genet Cytogenet. 134(2):142.
  3. Huret JL. (1991). Inv(16)(p13q22), t(16;16)(p13;q22), del(16)(q22). Atlas Genet Cytogenet Oncol Haematol.