Cancer staging systems are something pathologists ought to be familiar with.

Overview

Systems:

TNM staging system - most common, and used for the most common (adult) cancers.
World Health Organization (WHO) grading system - for CNS tumours.
Durie-Salmon system - multiple myeloma.
Ann Arbour system - for Hodgkin lymphoma and non-Hodgkin lymphoma (excluding mycosis fungoides and Sezary syndrome).
St. Jude system - pediatric pathology.

Score:

Most system are four tiered and use Roman numerals.
- Stage I: early cancer.
- Stage II: late early cancer (cancer between early and advanced stage).
- Stage III: advanced cancer - often defined by lymph node metastasis.
- Stage IV: late advanced cancer - often defined by metastasis.

TNM staging system

Name of the system comes from the elements: Tumour, Nodes (lymph nodes), Metastasis (distant).
Most common staging system.
Staging parameters dependent on the specific site.

Table of modifiers:^[1]

Modifier	Meaning	Example	Notes
m	multiple tumours	pT(m)NM or pT2(2)N0Mx	tumour stage = highest stage of all the individual tumours
c	clinical stage	cTNM	if it is not specified clinical is assumed
p	pathologic stage	pTNM	derived from a surgical specimen or biopsy
a	stage at autopsy	aTNM	malignancy was not staged previously or treated - unless otherwise specified
y	staging after therapy	ypTNM	do not try to estimate pretreatment stage
r	recurrent tumour stage	rTNM	must have a clinically documented disease freedom

Usually determined by one of the following:

Other factors:

Lymphovascular invasion usually does not affect the tumour stage.
- Exceptions:
  - Seminoma.
  - Intrahepatic bile duct carcinoma.
  - Hepatocellular carcinoma.^[2]
Margin status usually does not affect the tumour stage.
- Exception:
  - Prostate adenocarcinoma - bladder neck margin positivity.

Lymph node involvement.
Positive lymph nodes (without mets) often upstage to stage III.
- May upstage to stage II in some tumours.
Sampling may be selective (sentinel lymph nodes).