MYC amplification means a cancer cell has extra copies of the **MYC** gene. Extra copies can increase MYC activity and push cells to grow and divide. It is most often discussed as a **tumor biomarker** found through pathology and molecular testing. Clinicians use it to help describe tumor biology and support diagnosis and planning in some cancers.

RB1 loss means a cancer cell has lost normal function of the RB1 gene or its protein product. RB1 is a tumor suppressor gene that helps control how cells move through the cell cycle. In oncology, RB1 loss is most often discussed as a biomarker found on tumor testing. It is used to help describe tumor biology and sometimes guide treatment planning.

A TP53 mutation is a change in the TP53 gene, which helps cells prevent damaged DNA from turning into cancer. In cancer care, it is most often discussed as a tumor (somatic) finding on molecular testing. It can also be inherited (germline) in some people, which changes cancer risk and screening needs. Clinicians use TP53 mutation results to help describe tumor biology and guide parts of diagnosis and treatment planning.

A TERT promoter mutation is a DNA change in a gene control region that can increase telomerase activity in tumor cells. It is not a treatment, but a molecular finding used in cancer diagnosis and tumor profiling. It is most commonly identified through tumor genomic testing on biopsy or surgical specimens. Clinicians use it to help classify cancers, refine prognosis in some settings, and support treatment planning.

MGMT methylation is a laboratory finding that describes a chemical “tag” on DNA in tumor cells. It most often refers to methylation of the MGMT gene promoter, which can reduce MGMT protein production. It is commonly used in neuro-oncology, especially in gliomas such as glioblastoma, to help interpret likely treatment response. It is one piece of information used alongside imaging, pathology, and other molecular markers.

PTEN loss means a tumor has reduced or absent function of the PTEN tumor-suppressor gene or its protein. It is most often described in pathology or molecular testing reports for cancer. Clinicians use PTEN loss as a biomarker to help characterize a tumor and understand its behavior. Its clinical significance can vary by cancer type and stage.

TSC2 testing looks for changes (variants or mutations) in the **TSC2 gene**. It may be done on **blood or saliva** to evaluate inherited risk, or on **tumor tissue** to evaluate cancer-related changes. It is most commonly used in the evaluation of **tuberous sclerosis complex (TSC)** and in selected tumors linked to the **mTOR growth pathway**. In oncology, it can be part of broader **molecular profiling** to help characterize a tumor and explore treatment options.

TSC1 testing looks for changes (variants or mutations) in the **TSC1 gene**. It is most often performed using a blood or saliva sample (germline testing) or a tumor sample (somatic testing). In cancer care, it commonly appears as part of broader tumor genomic profiling panels. It can also be used when clinicians suspect **tuberous sclerosis complex (TSC)** or related conditions.

FGFR alteration testing is a laboratory method used to look for changes in FGFR genes within cancer cells. These changes can help explain what is driving a tumor’s growth. The results may support diagnosis and may help clinicians consider targeted therapies or clinical trials. It is most commonly used in oncology as part of tumor genomic profiling on biopsy or surgical tissue, and sometimes on blood (“liquid biopsy”).

ESR1 mutation is a change in the **ESR1 gene**, which provides instructions for making the **estrogen receptor**. It is most commonly discussed in **estrogen receptor (ER)-positive breast cancer**, especially in advanced or metastatic disease. Clinicians use ESR1 mutation results to understand **tumor biology** and help guide **treatment selection**. Testing may be done on tumor tissue or through a blood-based “liquid biopsy” that looks for tumor DNA.