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CBFB t

(16;16), inv (16)

F CBFB

Assocations:

Acute Myelogenous Leukemia (M4eo)

CPT Code:

88367 x2 - Morphometric analysis

Turnaround Time:

3 days

Methodology:

Fluorescence in situ hybridization (FISH)

Specimen Requirements:

  • 5.0ml (min. 3.0 ml) peripheral bloodin sodium heparin preferred, EDTA accepted
  • 3.0ml (min 1.0ml) bone marrow in sodium heparin preferred, EDTA accepted
  • 5mm3 fresh tissue in MPLN RPMI media
  • 3.0ml (min 2.0ml) FNA in MPLN RPMI  media

    • Causes for Rejection:

    Clotted specimen; specimen exposed to extreme temperature; anticoagulant toxic to cells; insufficient number of cells

    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 and Handling:

    Whole blood and bone marrow ship ambient

    Fresh tissue or FNA ship in a styrofoam container with an ice pack (do not allow ice pack to directly contact sample)

    Reference Range:

    2> FISH results indicate whether rearrangement is present or absent

    Indication:

    Structural abnormalities of chromosome 16 involving the CBFB locus have been identified in a specific group of patients with acute myelomonocytic leukemia 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. 

    The FISH probe for CBFB is a dual color rearrangement probe that identifies structural abnormalities of chromosome 16 in interphase cells or in metaphase spreads.  These abnormalities include pericentric inversions of chromosome 16 (inv 16) and translocations between the chromosome 16 homologues referred to as t(16;16).  The normal pattern for this probe is the presence of two yellow (fused orange/green) signals - one signal on each chromosome 16.  In interphase cells an abnormal pattern is represented by one fusion signal, one orange signal, and one green signal.  This pattern does not discriminate between the inversion and the translocation in interphase cells. In metaphase spreads, cells with the inverted 16 show separate orange and green signals on opposite arms of the abnormal 16 and a yellow fusion signal on the normal 16.  Metaphase spreads with the t(16;16) will have one chromosome 16 showing a fused signal on one arm and a green signal on the other arm; the other 16 shows a single red signal.  Use of the CBFB probe on metaphase spreads will also facilitate the identification of variant translocations involving 16q22 and the detection of deletions related to inversions of chromosome 16.

    References:

    1. 1. Huret JL. Inv(16)(p13q22), t(16;16)(p13;q22), del(16)(q22). Atlas Genet Cytogenet Oncol Haematol, June 1999. URL:http://www.infobiogen.fr/services/chromcancer/Anomalies/inv16.html

    2. 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.
    3. 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.