Still on vacation, hence slow answer. Looks like the discussion progressed according to the following lines:
Condition vs. Observation: According to the OMOP definition everything that defines the diseased state reported by the physician (diagnosis) or patient (sign, symptom) is a Condition. So, let’s not use Observations in here. That table should really be called GARBAGE_CAN because it contains everything that is not a condition, or a measurement, or a procedure, or a drug, or a device. So, if we are trying to solve the oncology problem we should model this properly where it belongs (the CONDITION table).
Pre vs. post-coordination. I think we all agree that we cannot pre-coordinate the entire definition of a cancerous disease of a patient into a single code. Which means we have to do some post-coordination. Currently, the model does not allow true post-coordination (lining up a random number of codes with some logic between them). And I don’t know what SNOMED has in mind because @Vojtech_Huser’s link is dead. So, the only way I see is to add fields, that together with the condition_concept_id form the complete cancer record. How about this:
Wrt LOINC: Not sure how this helps us. All they did is to give a LOINC number to each choice of a panel. Makes it a little easier to ETL stuff into the vocabulary, but those panels aren’t exactly user-friendly if you want to find, say, stage IV amelanotic melanomas, unless you really know them by heart.