Table 4

 The use of reporting categories for small volume nodal involvement

CategoryProportion of respondents using itNo of different interpretations given for the categoryComments
*For ease, no distinction was made between replies with an upper limit of 2 mm not including this value (<2 mm) and those including this value (⩽2 mm). †Definitions inclusive or non-inclusive of this value lumped together. ‡A few of these also giving some descriptive supplements such as location in the parenchyma or in afferent vessels or sinuses.
IHC, immunohistochemistry; ITC, isolated tumour cell.
Micrometastasis222/240 (93%)1771/202 (35%) referring to or in keeping with the 6th edition of the TNM system (with 0.2 mm lower cutoff value)*3–5
76/202 (38%) using only the 2 mm upper limit*, in accordance with earlier TNM definitions6,7
18/202 (9%) referring to the TNM system without mentioning the edition (either using the 0.2 mm lower cutoff value or not)
37/202 (18%) using heterogeneous definitions not in accord with TNM definitions
No definitions given by 20 laboratories
ITC171/240 (71%)1065/155 (42%) referring to the 6th edition of TNM classification,4,5 or using its definitions, or giving an upper limit of 0.2 mm†
49/155 (32%) stressing the isolated or single nature of the tumour cells in the definition, some requiring other criteria too (such as localisation in sinuses); 10 units from this last group defining ITC by “isolated tumour cells”, others using different wording
14/155 (9%) stressing detection by IHC
9/155 (6%) defining ITC by the presence of the cells in the sinuses or afferent lymphatics
18/155 (12%) giving maximum number of cells that could fit in their category of ITC; these numbers demonstrated a wide variety, including up to 2, 3, 4, 5, 6, 10, or 20 cells
No definitions given by 16 laboratories
Submicrometastasis53/240(22%)724/47 (51%) using an inclusive or non-inclusive upper limit of 0.2 mm‡
7/47 (15%) reporting definitions close to the TNM definition of micrometastasis, which may represent misreading of the given category
16/47 (34%) giving very heterogeneous definitions, including IHC detected or confirmed cells, <1 mm, 10 cells to 2 mm, 50–100 cells, clusters, etc
No definitions given by 6 laboratories