How does one classify single tumour cells detected immunohistochemically in lymph nodes?
There has been considerable debate in recent years on how to classify tumour cells in lymph nodes or bone marrow that are detected by immunohistochemical or molecular methods. An optional proposal to deal with this situation as subsets of N0. Single tumour cells should be distinguished from cases with morphologic evidence of micrometastasis, i.e., no metastasis larger than 0.2 cm [3]. The latter can be identified by the addition of (mi) in the pN or pM categories as follows: pN1 (mi) = Regional lymph node micrometastasis pM1 (mi) = Distant micrometastasis 1.
