Chemotherapy response score: summary of criteria
| CRS | Criteria |
| CRS1: No or minimal tumour response | Mainly viable tumour with no or minimal regression-associated fibroinflammatory changes* limited to a few foci. Note: cases in which it is difficult to decide between regression and tumour-associated desmoplasia or inflammatory cell infiltration |
| CRS2: Partial tumour response | Appreciable tumour response amidst viable tumour, both readily identifiable and tumour regularly distributed. Note: cases ranging from multifocal or diffuse regression-associated fibroinflammatory changes*, with viable tumour in sheets, streaks or nodules, to extensive regression associated fibroinflammatory changes* with multifocal residual tumour which is easily identifiable |
| CRS3: Total or near-total tumour response | No residual tumour OR minimal irregularly scattered tumour foci seen as individual cells, cell groups or nodules up to 2 mm in maximum size. Note: cases showing mainly regression-associated fibroinflammatory changes* or, in rare cases, no/very little residual tumour in complete absence of any inflammatory response; advisable to record whether ‘no residual tumour’ or ‘microscopic residual tumour present’ |
*Regression-associated fibroinflammatory changes: fibrosis associated with macrophages, including foam cells, mixed inflammatory cells and psammoma bodies; to distinguish from tumour-related inflammation or desmoplasia.
CRS, chemotherapy response score.