CPT® Code 81206

Molecular genetic testing is a critical diagnostic tool used to identify specific mutations in the BCR/ABL1 gene, which are commonly associated with chronic myelogenous leukemia (CML). This testing focuses on a particular genetic alteration known as a reciprocal translocation, designated as t(9;22). This translocation involves the BCR (breakpoint cluster region) gene located on chromosome 22, often referred to as the Philadelphia chromosome, and the ABL1 (V-abl Abelson murine leukemia viral oncogene) gene found on chromosome 9. The resulting fusion gene from this translocation encodes a tyrosine kinase that is unregulated and targets the cytoplasm, leading to uncontrolled cell proliferation even in the absence of cytokine signals. This mechanism significantly increases the risk of developing certain types of cancers, particularly CML. At the time of initial diagnosis, karyotyping and molecular testing techniques, such as reverse transcription polymerase chain reaction (rtPCR) or fluorescence in situ hybridization (FISH), are essential for defining tumor markers. These markers are crucial for monitoring residual disease during and after treatment. The BCR gene contains three distinct breakpoint cluster regions, and the specific code 81206 is utilized to identify the major breakpoint, which occurs at p210 within a 5.8 kb major breakpoint cluster region (M-bcr) around exon b3. This major breakpoint results in the formation of a BCR-ABL1 p210 chimeric transcript, where BCR is fused at exon b2 or b3 with ABL1 exons 2 through 11. For identification of a minor breakpoint, which occurs at p190 in the minor breakpoint cluster region (m-bcr) on intron 1, the code 81207 is used. This minor breakpoint leads to the fusion of BCR exon 1 with the same ABL1 exons. Additionally, the code 81208 is designated for identifying other breakpoint cluster regions that are not classified as major or minor.