Using MeSH Qualifiers to Weave Together a Concept When No Exact MeSH Term Exists

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Medical Subject Headings (MeSH), the National Library of Medicine’s controlled vocabulary thesaurus, makes comprehensive searching of the biomedical literature indexed in the MEDLINE/PubMed database immensely easier. Rather than require the searcher to guess how various authors from around the world may have referred to a particular concept, the indexers of the articles determine what each article is about and then apply the preferred MeSH terms accordingly to make each article more findable.

But what happens if a spot-on MeSH term for what you are looking for does not exist? That’s where MeSH qualifiers, otherwise known as MeSH subheadings, really show their value. Here’s an example to illustrate the need filled by MeSH subheadings:

Say you were interested in conducting a comprehensive search to identify studies looking at:  “a particular primary cancer (that has been surgically resected) metastasizing to a secondary site”

Breaking this search down into individual concepts, you have:
i) a primary cancer type, ii) surgical resection, iii) cancer metastasis, and iv) a secondary cancer type

When you try to map these to the available MeSH terms, you may consider these options:

“Neoplasms, Unknown Primary”[Mesh]: https://www.ncbi.nlm.nih.gov/mesh/68009382

“Neoplasm Metastasis”[Mesh]: https://www.ncbi.nlm.nih.gov/mesh/68009362

“Lymphatic Metastasis”[Mesh]: https://www.ncbi.nlm.nih.gov/mesh/68008207

“Surgical Procedures, Operative”[Mesh]: https://www.ncbi.nlm.nih.gov/mesh/68013514

However, if you look closely at how some relevant articles are indexed by MEDLINE, you will notice that the indexers likely passed on the options above and instead made use of the available subheadings to be more specific.

For example, this paper: “Risk factors for the development of metachronous bone metastasis in colorectal cancer patients after curative resection.” is indexed as follows:

  • Bone Neoplasms/secondary*
  • Colorectal Neoplasms/pathology*
  • Colorectal Neoplasms/surgery*

While this paper, where the surgery was done on the secondary cancer type instead, “Effect of Surgery on Quality of Life of Patients with Spinal Metastasis from Non-Small-Cell Lung Cancer.” is indexed as:

  • Carcinoma, Non-Small-Cell Lung/pathology*
  • Lung Neoplasms/pathology*
  • Spinal Neoplasms/secondary*
  • Spinal Neoplasms/surgery*
  • Spine/surgery*

In summary: The subheading “secondary” is added to the MeSH term for the type of cancer where the cancer metastasized to (ie. “used with neoplasms to indicate the secondary location to which the neoplastic process has metastasized”). There is no subheading for “primary” so instead the subheading “pathology” is generally applied to the primary cancer type MeSH term. The “surgery” subheading is “used for operative procedures on organs, regions, or tissues in the treatment of diseases, including tissue section by lasers – it excludes transplantation, for which “transplantation” is used.” so it is added to whichever cancer type (the primary or secondary) that was surgically resected. Having MeSH qualifiers/subheadings available no doubt increases the searcher’s ability to reach a greater level of specificity than could be achieved by just using the MeSH terms alone.

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