Stage is how far it has spread; grade is how abnormal it looks
Expansion
Stage: the anatomical extent of disease
- TNM: Tumour size and local extent, Nodal involvement, Metastasis
- Older systems persist in some tumours, such as Dukes for colorectal and Ann Arbor for lymphoma
Grade: the histological differentiation
- Well, moderately or poorly differentiated, or numeric grades
- Based on the resemblance to the tissue of origin, nuclear pleomorphism and mitotic count
- Tumour-specific systems: Gleason for prostate, Nottingham for breast, Fuhrman for renal
Stage generally outweighs grade in prognostic value and is the main determinant of treatment.
Two important qualifications. Prostate cancer is the notable exception where grade (Gleason score) carries exceptional weight. And molecular characteristics increasingly matter more than either: oestrogen receptor and HER2 status in breast cancer, KRAS and mismatch repair status in colorectal cancer, and EGFR and ALK in lung cancer all determine treatment independently of stage and grade.
Carcinoma in situ is by definition stage 0: dysplastic cells filling the epithelium but not breaching the basement membrane, and therefore incapable of metastasis.