The short answer
PTEN is a tumor suppressor gene. Its protein sits in a pathway that tells cells to stop dividing and to self-destruct when they should. Loss on a report means that brake looks absent or damaged in the sample tested, and the first question is whether the finding is tumor-only or inherited.
PTEN is a tumor suppressor gene, and its protein signals cells to stop dividing and triggers cell self-destruction.
Loss can be reported from a stain, which looks for the protein, or from sequencing, which reads the gene. They are not the same test.
Somatic PTEN mutations are among the most common genetic changes found in human cancers.
Inherited PTEN changes cause a group of conditions known as PTEN hamartoma tumor syndrome, and need separate germline testing to confirm.
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A brake that appears to be missing
PTEN is a tumor suppressor gene. MedlinePlus Genetics says its enzyme helps keep cells from growing and dividing too fast or in an uncontrolled way. It is part of a chemical pathway that tells cells to stop dividing and tells them to self-destruct, a process called apoptosis.
So "loss" means that, in the sample tested, that brake looks absent or broken.
Different tests can produce the same word
Reports often do not say which test found the PTEN result. One kind of test looks at the protein in tissue. Another reads the gene itself. Ask which method produced yours.
How common it is, and where it shows up
MedlinePlus Genetics says acquired (somatic) PTEN mutations are among the most common gene changes found in human cancers. It names these cancers:
- endometrial cancer, cancer of the womb lining
- glioblastoma and astrocytoma, two kinds of brain tumor
- melanoma, a skin cancer
- prostate cancer, where studies suggest PTEN changes may be the most frequent gene change
For prostate cancer, MedlinePlus adds that PTEN mutations are linked with more advanced stages of tumor growth. That is a pattern across groups, not a forecast for one person.
Tumor test, or inherited test?
NCI says biomarker testing is different from genetic testing for inherited mutations. It adds that some biomarker tests can find genetic changes you were born with. When that happens, genetic counseling may be recommended.
Inherited PTEN changes exist. MedlinePlus Genetics links them to conditions such as Cowden syndrome. These involve multiple hamartomas (benign growths) and a higher risk of some cancers, especially breast, thyroid, and uterine lining cancer. MedlinePlus also says inherited PTEN changes account for only a small fraction of all breast cancer cases.
If you wonder whether a result could run in your family, ask your care team about genetic counseling.
What it changes about treatment
NCI notes that biomarker testing can help you find a study of a new cancer treatment that you may be able to join.
MedlinePlus Genetics reports one drug link. Loss of working PTEN enzyme is related to poor response to trastuzumab (Herceptin), a breast cancer drug. Ask your team whether any result on your report is driving your plan.
Biomarker Testing and Precision Medicine explains how these reports get used. Genetic Testing vs Genomic Testing covers the inherited and tumor-only split in more depth.
Sources
Common questions
Does PTEN loss mean my cancer is aggressive?
Not by itself, and it varies by cancer type. MedlinePlus Genetics notes that in prostate cancer, PTEN mutations are in some cases associated with more advanced stages of tumor growth. It is one feature of the tumor, read alongside everything else on the report.
Is this something I inherited?
Tumor testing cannot tell you on its own. NCI says biomarker testing is different from genetic testing used to find inherited mutations, though some biomarker tests do pick up changes you were born with. Confirming an inherited change needs separate germline testing.
What is the difference between loss of staining and a deletion?
A stain looks for the PTEN protein in tissue. Sequencing reads the gene itself. Absent protein and a deleted gene often go together, but they are separate observations from separate methods, and your report should say which was done.
Does a PTEN result change my treatment?
Often not directly. There is no standard treatment keyed to PTEN in the way there is for some other markers. NCI notes that biomarker testing can help identify a clinical trial you may be able to join, which is where PTEN status more often matters.
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Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes, and this is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and then compared with the sources listed on it, looking for statements those sources do not back up. That check is not a sentence-by-sentence record and can miss errors. It is not a medical review, and it does not confirm the page is complete or right for your situation.
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