Combining morphologies

When modeling a concept requiring two role groups with the same finding site/body structure but two different morphologies (because a combined morphology does not exist), then those two morphologic abnormalities can be combined to create a new single, combined |(morphologic abnormality)| concept. Keep the newly created morphologic abnormality concept primitive as all morphologic abnormality concepts should be primitive. Limit the combination to two morphological concepts into a single concept; combining more than two morphological concepts into a single combined concept is not permitted.

For example, If 400067002 |Acantholytic epidermal nevus (disorder)| had the same Finding site of |Skin structure (body structure)| with two different morphologic abnormalities of |Epidermal nevus (morphologic abnormality)| and |Acantholysis (morphologic abnormality)|, then those two morphologic abnormality concepts can be combined to create a single, primitive, morphologic abnormality concept of |Acantholytic epidermal nevus (morphologic abnormality)|. This will prevent modeling with two relationship groups.

Instead of modeling as per this diagram in the stated view with two morphologies of the same finding site:

Model as in the stated view of this diagram with a combined morphology:

Morphologies can be combined to create a single morphologic abnormality concept where doing so creates a specialization of the morphology e.g. 55075001 |Bleeding ulcer (morphologic abnormality)|. Where morphologies are different e.g. abscess and cellulitis, they can not be combined.

This guidance is not being applied retrospectively so the concept 707496003 |Inflammation and consolidation (morphologic abnormality)| will be an exception to this rule as it already exists as a current concept.

Combining morphologies to create a specialization is done when modeling a concept that requires two role groups with the same body structure and two morphology values. Creating a combined morphology concept enables one role group to be used.

Older 'like' content may still use the two role groups. This content would also need to use the new combined morphology value to support correct subsumption.

Neoplasm exception

Subtypes of 108369006 |Neoplasm (morphologic abnormality)| are not to be combined. These morphologies represent histological cell types that are recognized internationally by pathologists, classified by WHO, and aligned with the ICD-O classification.

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