Knowledge Representation Model

The underlying principle of the Cancer Synoptic Reporting Project Group is that the "question" (represented by a SNOMED CT observable entity) should include all the context needed to clearly understand the "answer" (or observation) that is recorded. The criteria for deciding these results depend on additional information and knowledge that can't be conveyed by SNOMED CT alone, such as clinical guidelines.

For example, the differentiation between an adenocarcinoma and a mucinous adenocarcinoma is based on the amount of mucin measured in the cells and the organ system involved.  In breast tissue, the amount of mucin in the cells to be considered a mucinous adenocarcinoma is > 80% but in the colon is > 50%. The pathologist is responsible for this knowledge, not SNOMED CT. So, this type of explicit knowledge of the pathologist is outside of the scope of the SNOMED CT concepts, and will not be discussed further in this document.

The observable entity/observation pairs below each state that the histologic type of the neoplasm assessed is a mucinous adenocarcinoma in the breast and in the colon.  It is the SNOMED CT observable entity that provides the context for the observation, specifically the organ system of concern.  It does not directly state the amount of mucin in the cells as observed by the pathologist.  The pathologist exercised domain-specific knowledge to reach such a conclusion. 

Mucinous adenocarcinoma of the breast: 1660001000004100 |Histologic type of primary malignant neoplasm of breast (observable entity)|  =   72495009 |Mucinous adenocarcinoma (morphologic abnormality)|    reflects the pathologist's interpretation of the microscopically evaluated slides that the percent tumor cells containing mucin as a proportion of the total number of tumor cells is > 80%.

Mucinous adenocarcinoma of the colon: 1284862009 |Histologic type of primary malignant neoplasm of cecum and/or colon and/or rectum (observable entity)|  =  72495009 |Mucinous adenocarcinoma (morphologic abnormality)|  reflects the pathologist's interpretation of the microscopically evaluated slides that the percent tumor cells containing mucin as a proportion of the total number of tumor cells is > 50%.

Therefore, it is important to understand that the observable entity/observation pairs used throughout the cancer pathology synoptic reporting use cases reflect point in time observations as ultimately assessed and interpreted  by the pathologist. Domain knowledge specific to the practice of pathology and oncology is NOT intended to be represented by the terminology, but rather, the terminology represents what the observation was and is based on specific domain expertise.

Neoplasm Characteristics to be Measured

As noted, the synoptic pathology report is comprised of a list of characteristics of the neoplasm that are required to be observed and reported by the pathologist.  Each characteristic is modelled using the 363787002 |Observable entity (observable entity)| hierarchy and concept model. 

Major categories of neoplasm characteristics required in each report are listed below. 

• Procedure used to collect the specimen(s)
• Tumor site
• Tumor dimensions 
• Histologic type
• Histologic grade
• Anatomic location(s) involved by direct, contiguous extension of the neoplasm
  • Tissue layers
  • Adjacent tissue structures
  • Lymph/vascular invasion
  • Perineural invasion
• Presence of neoplasm at surgical margins
• Lymph node metastasis
  • Number lymph nodes involved by metastasis
  • Number lymph nodes examined
  • Location of lymph nodes
• Anatomic locations involved by metastatic, discontinuous spread of the neoplasm
• TNM staging (Tumor, Node, Metastasis)

Observations to be reported

The list of possible observations that can be made for each characteristic is comprised of a constrained list of acceptable observations (i.e., value sets).  For example, a list of acceptable histologic types (morphologic abnormalities) is provided to the pathologist to select when reporting the histologic type of the neoplasm.  Semantic types of these value sets are dependent upon the |Property| target value.

Semantic types in a response value set are all of the same semantic type with the exception of the use of |Qualifier value| concepts employed for pathologist observations such as 385432009 |Not applicable (qualifier value)|  or  1156316003 |Cannot be determined (qualifier value)| .

For example, the concept, 911750741000004104 |Histologic type of primary malignant neoplasm of lung (observable entity)| , is modeled with  370130000 |Property (attribute)|  =  6030001000004102 |Histologic type (property) (qualifier value)| .  The range of possible observations must be << 1240414004 |Malignant neoplasm (morphologic abnormality)| . 

In addition to the template constraints, the protocol publishers further constrain the acceptable value sets to include only those values that are possible for a particular malignant neoplasm.   For example, the possible values for histologic types in the lung protocol would never contain values for Germ cell neoplasms (a condition only possible in reproductive organs).