CPT® Code 81540

Oncology (tumor of unknown origin), mRNA, gene expression profiling by real-time RT-PCR of 92 genes (87 content and 5 housekeeping) to classify tumor into main cancer type and subtype, utilizing formalin-fixed paraffin-embedded tissue, algorithm reported as a probability of a predicted main cancer type and subtype

The CPT® Code 81540 pertains to a specialized molecular genetic testing procedure designed for the classification of tumors of unknown origin, specifically carcinoma of unknown primary site (CUP). This testing utilizes formalin-fixed paraffin-embedded tissue samples, which are commonly used in histopathology. The procedure involves the analysis of messenger RNA (mRNA) extracted from the tissue, which is then converted into complementary DNA (cDNA) through a process known as real-time reverse transcription polymerase chain reaction (RT-PCR). This assay evaluates the expression profiling of a total of 92 genes, comprising 87 content genes and 5 housekeeping genes. The primary objective of this testing is to classify the tumor into its main cancer type and subtype, thereby aiding in the diagnostic process. CUP presents a unique challenge in oncology, as tumors may manifest in various locations, often indicating an aggressive nature and a wide range of potential diagnoses. Traditional diagnostic methods, such as immunohistochemical (IHC) staining, provide limited insights into the tumor's origin. However, when combined with genetic expression profiling, the likelihood of identifying a specific treatment approach tailored to the tumor's characteristics is significantly enhanced. The results of this genetic testing yield a probability score that indicates the likelihood of the tissue sample correlating with a particular tumor origin and histological subtype, ultimately supporting more informed clinical decision-making and potentially improving patient outcomes.