CPT® Code 81504

Oncology (tissue of origin), microarray gene expression profiling of > 2000 genes, utilizing formalin-fixed paraffin-embedded tissue, algorithm reported as tissue similarity scores

Microarray gene expression profiling is a sophisticated molecular biology technique that enables the simultaneous analysis of the expression levels of thousands of genes. This process is particularly valuable in oncology, as it aids in the precise classification of tumors and enhances the prediction of clinical outcomes for patients. The procedure involves the use of formalin-fixed paraffin-embedded tissue samples, which are commonly utilized in histopathology. In this test, predefined DNA oligonucleotide probes are chemically bonded to a solid surface, typically a glass slide, creating what is known as a gene chip. The tissue sample is processed to extract messenger RNA (mRNA), which is then labeled with a fluorescent marker. This labeled mRNA is hybridized to complementary DNA (cDNA) sequences present on the gene chip. Following hybridization, the gene chip is scanned to identify the presence and intensity of the fluorescent signals at each probe-target hybridization site. The intensity of the fluorescence at these specific locations provides quantitative data regarding the expression levels of the corresponding genes. Advanced computer algorithms analyze this data to compare the gene expression profile of the patient's tissue sample against a comprehensive database of tumor samples, ultimately generating tissue similarity scores that reflect the degree of similarity between the samples. This information is crucial for oncologists in making informed decisions regarding diagnosis and treatment strategies.