CPT® Code 81120

The CPT® Code 81120 pertains to the analysis of the IDH1 gene, specifically focusing on common variants such as R132H and R132C, which are associated with glioma tumors. Gliomas represent the most prevalent category of primary brain tumors, originating from glial cells that provide support and protection to neurons within the brain and spinal cord. These tumors can be classified into various types, including astrocytomas, ependymomas, and oligodendrogliomas, each with distinct characteristics and implications for treatment and prognosis. The analysis of the IDH1 gene is crucial as it plays a significant role in the metabolic processes of cells. The IDH1 gene is located on the long (q) arm of chromosome 2 at position 34, while the IDH2 gene is found on the long (q) arm of chromosome 15 at position 26.1. The enzymes produced by these genes, isocitrate dehydrogenase 1 and 2, are responsible for converting isocitrate into 2-ketoglutarate, a process that also generates NADPH, a molecule essential for cellular protection against oxidative stress. Mutations in the IDH1 and IDH2 genes disrupt the normal function of these enzymes, leading to the abnormal accumulation of D-2-hydroxyglutarate, which interferes with cell maturation and promotes the proliferation of immature cells, ultimately contributing to the development of glioma tumors. The testing process involves obtaining tumor tissue samples through a separate, reportable procedure, followed by the extraction of DNA from the tumor cells. This DNA is then amplified using polymerase chain reaction (PCR) techniques with specific primers targeting IDH1 codon 132 and IDH2 codon 172. The final step involves pyrosequencing the cell sample to detect the presence or absence of any gene mutations, providing critical information for prognosis and potential treatment strategies.