ALK 2p23 by FISH

F ALK


Test Synonym:
Anaplastic Lymphoma Kinase gene rearrangement



CPT Code:
88367x2 - Morphometric analysis, in situ hybridization, automated
or

88368 x2 - Morphometric analysis, in situ hybridization, manual


Turnaround Time:
3 days



Methodology:
Fluorescence in situ hybridization (FISH)



Specimen Requirements:

• 2.0 ml (min. 1.0 ml) peripheral blood in sodium heparin, EDTA accepted
• 1.0 ml (min. 0.5 ml) bone marrow in sodium heparin, EDTA accepted
• 5 mm3 fresh tissue in MPLN RPMI media
• 3.0 ml (min. 2.0ml) FNA in MPLN RPMI media
• 10% neutral buffered formalin fixed paraffin embedded tissue


Causes for Rejection:

Clotted specimen; Specimen exposed to extreme temperature; Anticoagulant toxic to cells; insufficient number of cells; Improper fixative



Specimen Stability:

• Peripheral blood and bone marrow stable at 18-25°C for 72 hours
• Fresh tissue or FNA stable at 2-8°C for 72 hours


Storage and Handling:
• Whole blood and bone marrow ship ambient
• Fresh tissue, FNA or paraffin embedded tissue ship in a Styrofoam container with an ice pack (do not allow ice pack to directly contact sample)


Reference Range:
 FISH results indicate whether rearrangement is present or absent. FISH for ALK is performed using a Dual Color rearrangement probe.

In a normal cell with two intact copies of chromosome 2, two yellow (orange/green fused) signals will be seen.

In a cell with a translocation involving ALK, one orange and one green signal will be seen indicating the disruption of the ALK gene. One yellow signal will also be seen representing the normal chromosome 2.

Indication:
Anaplastic large cell lymphomas represent 20-50% of large cell lymphomas in children and 2-8% of non-Hodgkin lymphomas in adults. Translocations involving the ALK locus at 2p23 occur in about 50% of anaplastic large cell lymphomas. In most cases ALK expression is the result of a translocation between 2p23 and 5q35 that results in expression of a unique NPM-ALK protein. Several other chromosomes have been involved in translocation with 2p23 although at a much lower incidence than the t(2;5). Inversion of chromosome 2 can also result in rearrangements of ALK. Although ALK+ tumors are typically aggressive, they are associated with a favorable prognosis. Atypical cases with peripheral blood involvement have a poor prognosis.

The ALK assay on interphase cells does not identify the partner chromosome involved in the rearrangement. Routine chromosome studies or FISH on metaphase cells can aid in the identification of the second chromosome.

References:

  1. Huret JL: (2003) Anaplastic large cell lymphoma (ALCL). Atlas Genet Cytogenet Oncol Haematol
  2. Onciu M et al. (2003). ALK-positive anaplastic large cell lymphoma with leukemic peripheral blood involvement is a clinicopathologic entity with an unfavorable prognosis. Am J Clin Pathol 120(4):617
  3. Liang X et al. (2004). Assessment of t(2;5)(p23;q35) translocations and variants in pediatric ALK+ anaplastic large cell lymphoma. Am J Clin Pathol 121(4):496
  4. Benharroch D et al. (1998). ALK-positive lymphoma: a single disease with a broad spectrum of morphology. Blood 91(6):2076