This may fit here, or create a separate section under specification to describe the use case in particular - it is not clear from reading just this IG who the originator of this FHIR bundle is expected to be - the EHR-s, the LIS, a data mart, HIE? That would also help clarify the relationship woth other standards used in the laboratory data exchange paradigm.

The NAACCR IG section 1.3. STANDARDS AND GUIDELINES FOR ELECTRONIC TRANSMISSION OF REPORTS FROM PATHOLOGY LABORATORIES TO CENTRAL CANCER
REGISTRIES makes this very clear a statement like this should be added here:

The sope of this IG is to define the format for transmitting electronic pathology laboratory reports from pathology laboratories to central cancer registries.