This page is part of the MII IG Kerndatensatz-Modul Onkologie (v2027.0.0-ballot.1: Release) based on FHIR (HL7® FHIR® Standard) R4. This is the current published version in its permanent home (it will always be available at this URL). For a full list of available versions, see the Directory of published versions

TNM Step by Step

This page explains the module's TNM model along one continuous course of treatment: a breast carcinoma from initial diagnosis through neoadjuvant chemotherapy and surgery to recurrence. Every station links to its example instances — same patient, same disease, five classifications.

The model in one sentence: a panel (TNM classification) bundles one T, N and M category observation each via hasMember; prefixes that change interpretation (y, r, a) sit as modifierExtension on the category; the method-of-determination prefix (c, p, u) sits as a regular extension on Observation.code.

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Station 1 — Initial diagnosis: cT3 cN1 cM0

Clinical classification from imaging and examination. All three categories carry the c prefix via the extension mii-ex-onko-tnm-cp-praefix — it documents how the finding was determined, without changing what the value means.

Panel · cT3 · cN1 · cM0

Station 2 — After core biopsy: cT4 cN1 cM0

The biopsy reveals chest wall infiltration: the T upgrade to cT4. It remains a clinical category — pathological classification (p) requires resection, not biopsy. The panel keeps referencing the unchanged cN1/cM0: categories are reused, not duplicated.

Panel · cT4

Station 3 — After neoadjuvant chemotherapy: ycT2 ycN0 cM0

Here the y prefix as modifierExtension (mii-ex-onko-tnm-y-praefix) enters: classification during/after multimodal therapy. ycT2 does not describe the same situation as cT2 — the tumour was shrunk therapeutically. That is precisely why it is a modifierExtension: systems that do not evaluate it must not silently interpret the value.

Panel · ycT2 · ycN0

Station 4 — After surgery: ypT0 ypN0 cM0 (pathological complete response)

Resection enables the pathological classification: p prefix in the cp extension, y prefix still as modifierExtension — ypT0 means: no residual tumour demonstrable in the resection specimen, after neoadjuvant therapy. The accompanying classifications join in: lymphatic invasion L0, venous invasion V0, perineural invasion Pn0 and the residual status R0.

Panel · ypT0 · ypN0

Station 5 — Recurrence: rcT2 cN1 cM1

Two years later, a local recurrence with distant metastasis. The r prefix as modifierExtension (mii-ex-onko-tnm-r-praefix) marks the recurrence classification; the categories themselves are clinical (c) again.

Panel · rcT2 · rcN1 · rcM1

The course as the bracket

Three follow-up instances (after chemotherapy, after surgery, recurrence) link the stations into the disease history via hasMember — oBDS chapter 17 in FHIR.

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What this page teaches about the modelling

• Categories are observations in their own right and are reused between panels, not copied (station 2).
• c/p/u is method, y/r/a is meaning: the former a regular extension on code, the latter a modifierExtension on the category — the rationale is on the Migration from v2026 page, entry 1.
• Prefixes combine: ypT0 carries p in the cp extension and y as modifierExtension at the same time (station 4).
• The deprecated symbol profiles (y/r/a/m as separate observations) deliberately no longer appear in this example; stored data using them stays readable — see Migration from v2026, entry 7.