The NCI Thesaurus is an ontology-like vocabulary that includes broad coverage of the cancer domain, including cancer related diseases, findings and abnormalities; anatomy; agents, drugs and chemicals; genes and gene products and so on. In certain areas, like cancer diseases and combination chemotherapies, it provides the most granular and consistent terminology available. It combines terminology from numerous cancer research related domains, and provides a way to integrate or link these kinds of information together through semantic relationships.

The Thesaurus currently contains over 34,000 concepts, structured into 20 taxonomic trees. The NCI Thesaurus provides concept history tables to record changes in the vocabulary over time as the science changes. Within NCI, the Thesaurus is used to provide terminology support to the Institutes public Web portal,, numerous portals supporting consortia and other communities of researchers, and is used in the caCORE as the semantic base for metadata and objects that form the infrastructure upon which the NCICB portals are built (see It is published under an open content license in a number of formats including OWL.


ncit.owl NCIt OBO Edition OWL format A direct transformation of the standard NCIt content using OBO-style term and ontology IRIs and annotation properties.
ncit.obo NCIt OBO Edition OBO format
ncit/ncit-plus.owl NCIt Plus This version replaces NCIt terms with direct references to terms from other domain-specific OBO Library ontologies (e.g. cell types, cellular components, anatomy), supporting cross-ontology reasoning. The current release incorporates CL (cell types) and Uberon (anatomy).
ncit/neoplasm-core.owl NCIt Plus Neoplasm Core This is a subset extracted from NCIt Plus, based on the [NCIt Neoplasm Core value set]( as a starting point.

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