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2025 MeSH Update and PubMed Year-End Activities

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At the end of each year, the National Library of Medicine (NLM) produces their annual updates to PubMed’s MeSH (Medical Subject Headings). These changes are made at every level of the MeSH infrastructure, including descriptors (headings or terms), qualifiers (subheadings), and supplementary concepts, and are made in response to changes in scientific discovery, taxonomy, ethical considerations, and published literature. The National Library of Medicine describes the necessity of these changes as this: “In biomedicine and related areas, new concepts are constantly emerging, old concepts are in a state of flux and terminology and usage are modified accordingly. To accommodate these changes, descriptors must be added to, changed or deleted from MeSH with adjustments in the related hierarchies, the Tree Structures.”

Types of MeSH Changes

  • Added Terms — brand new terms added, either as MeSH headings or Supplementary Concepts that currently do not warrant a full heading
  • Modified Terms — MeSH concepts that were changed (either name or hierarchical location), also referred to the the “Preferred Term“
  • Replaced Terms — Descriptors or Supplementary concept terms are replaced by another term; this can include Supplementary Concepts upgraded to Descriptors as well as merged terms
  • Merged Terms — Multiple Descriptor or Supplementary concept terms combined under a single concept term
  • Combined Terms — Descriptor and Qualifier (subheading) combination made into a new separate concept
  • Deleted Terms — Descriptor or Supplementary concept terms removed, due to either being combined, upgraded, or renamed

What’s New in 2025

Artificial Intelligence

The 2025 Annual MeSH Update includes a variety of important and much-needed changes. One of the biggest and most needed expansions in the 2025 update is to the Artificial Intelligence concept, including dozens of new MeSH Descriptors found within the broader concept, including:

Publication types

Several changes were made to publication types for MeSH 2025, including two new publication types:

Note: The NLM has made an exception to their general rule of not retroactively indexing; so just as they did in 2019 when “Systematic Reviews” became a separate publication type, citations will be retroactively updated to reflect these two new publication types.

The Network Meta-Analysis publication type was previously a Descriptor (MeSH Heading); thus for existing citations, the Descriptor term (“Network Meta-Analysis”[MeSH]) will be replaced with either the “Network Meta-Analysis”[Publication Type] OR “Network Meta-Analysis as Topic”[Mesh] as appropriate. This is an important change, as it extends the scope of indexing the publication type back to the introduction of the original term in 2017.

The “Scoping Review”[Publication Type] will replace either the “Review”[Publication Type] or “Systematic Review”[Publication Type] on appropriate citations extending back to 2020, the first year this term appears in MEDLINE. Additionally, “Scoping Review as Topic”[Mesh] has been expanded from the “Review as a Topic”[Mesh] term.

Additionally, NLM will discontinue indexing following Publication Type terms:

Note: As with previously discontinued Publication Types, which include “Government Publication,” “Newspaper Article,” “Overall,” and “Scientific Integrity Review,” these Publication Types will continue to exist in MeSH, appear on existing citations, and be searchable in PubMed. However, they will no longer be applied to new citations.

How Does this Impact Searching?

Since there are so many changes to MeSH terms and structure, if you save search strategies or search alerts, or want to rerun a search that was previously conducted (such as from a systematic review), these changes may impact if and how your search strategy functions. Below are some steps to take to ensure that your search strategy is not only viable but also the best reflection of the current database.

  1. Check search viability — Run your search in PubMed and go to Advanced Search and check if there are issues being highlighted in the Details section. Terms that were removed or modified (name changed, upgraded, merged, etc.) will likely be in red. If your search is suddenly retrieving no results, this also could be the cause.
  2. Identify relevant new terms — Refer to the New MeSH Descriptors for 2025 list to see if there are any relevant terms that were added for 2025 that may make your search strategy more robust or specific.
  3. Identify replaced terms — Refer to the MeSH 2025 – Replace Report to identify any terms that were replaced by another term, upgraded to Descriptors, or consolidated with another term.
  4. Review publication types — Refer to the Annual MeSH Processing for 2025 NLM Bulletin for changes to publication types

If you have searches saved in your My NCBI account and/or you are getting PubMed e-mail alerts, or if you need to update your Systematic Review based on your previous search strategy, you may want to consult a Research Informationist to ensure your saved searches are not affected by the annual changes in the MeSH terminology. Don’t hesitate to ASK US!

Important Note from NLM Regarding Reindexing

Typically, the NLM does not retroactively re-index MEDLINE citations with new MeSH heading concepts. Therefore, searching PubMed for a new MeSH term tagged with [mh] or [majr] effectively limits retrieval to citations indexed after the term was introduced. Searchers may consult the MeSH database to see the previous indexing terms most likely used for a particular concept before the new MeSH heading was introduced. For terms without previous indexing information, consider the next broader term(s) in the MeSH hierarchy. or more searching guidance, see the on-demand class MeSH Changes and PubMed Searching.

The New Role of RAS Genes in Cancer, Quitting Smoking Boosts Survival in Cancer Patients, and More

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  • In collaboration with other researchers, researchers at the National Institutes of Health discovered an entirely new ways RAS genes, which are “the second most frequently mutated genes in cancer”, drive cancer growth. The knowledge of RAS genes’ role in cancer was well established, but discovering how RAS genes trigger a chain “of events involving the transport of specific proteins in the nucleus” is an entirely new turn. The discovery can pave the way for new drug combinations to treat RAS-promoted cancers more effectively. The study was published in Nature Cancer.
  • Researchers from Washington University in St. Louis (WashU) conducted the phase I clinical trial of an investigational vaccine for the prevention of triple-negative breast cancer recurrence. This small clinical trial of a new type of vaccine, known as a neoantigen DNA vaccine, demonstrated promising, better-than-expected, results for patients with this aggressive, hard-to-treat, type of breast cancer. The study was published in Genome Medicine.
  • Another research that has implications for triple-negative breast cancer, among other cancer types, is conducted at Johns Hopkins University. This research is related to cancer cells that, after leaving the hypoxic (i.e., lacking oxygen) environment deep in the tumor, enter the bloodstream and spread. Scientists have identified 16 genes that breast cancer cells use to survive in the bloodstream. Each of these genes can become a therapeutic target to stop cancer recurrence, one of which has already been in clinical trials. The research was reported on in Nature Communications.
  • Researchers from Northwestern University have found an unexpected connection between COVID-19 infection and cancer regression. They discovered that the RNA from the SARS-CoV-2 virus that causes COVID-19 triggers the development of a unique type of immunity that can fight cancer. The discovery may lay a foundation for novel cancer treatments. The study was published in The Journal of Clinical Investigation.
  • Researchers from MD Anderson found significant survival benefits in patients who quit smoking after cancer diagnosis. “The best outcomes were observed in patients who started tobacco treatment within six months of a cancer diagnosis and were abstinent from smoking three months later.” The study was published in JAMA Oncology.

5-FU Acts Differently in Gastrointestinal Cancers, New Insights into Biology of Bladder Cancer and More

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  • A study by researchers from Rockefeller University provided a new insight into cancer biology by demonstrating that a lipid type is crucially essential for cancer immune evasion. The findings imply that existing medications for impeding lipid production can boost the immune system in fighting cancer. The study was published in Nature.
  • Researchers from Harvard Medical School and Massachusetts General Hospital showed that lung cancer screening guidelines by the U.S. Preventive Services Task Force don’t adequately serve their purpose, especially in Black patients. In place of requiring the equivalent of a pack a day for 20 years the Harvard researchers suggest switching “to a simple measure that would recommend annual screening for anyone who’s smoked for 20 years, regardless of how many cigarettes they smoke a day”. The study was published in the Journal of Clinical Oncology.
  • Unlike other breast cancer types, triple-negative breast cancer (TNBC) does not respond to hormone therapy or anti-HER2 drugs. A new study from Mass General Brigham established that combining two types of therapeutic agents (AKT and EZH2 inhibitors) can selectively kill these cancer cells, establishing a foundation for a new triple-negative breast cancer treatment. The study is published in Nature.
  • A study by Weill Cornell Medicine and the New York Genome Center has offered “unprecedented insights” into early bladder cancer (specifically, urothelial carcinoma) development. Researchers found that antiviral enzymes and standard chemotherapy were the main culprits for bladder cancer development as sources of mutations. The researchers also gained insights into the mechanisms of bladder cancer resistance to therapy. These findings are breakthrough contributions to the knowledge of bladder cancer biology and pave the way to new therapeutic strategies. The study was published in Nature.
  • Researchers from MIT discovered that the old cancer drug 5-fluorouracil (5-FU) which has been around since the 1950s, “acts differently in different types of cancer”. While it was long established that it affects cancer by damaging building blocks of DNA, the new study found that in gastrointestinal cancers it kills cells by interfering with RNA synthesis. This new finding will have an impact on what combinations of 5-fluorouracilwith with other chemotherapy drugs are given to achieve synergistic effects in different types of cancer. The study was published in Cell Reports Medicine.