Result

Application of the objective rule according to Josef Rüschoff, hence the change to a higher magnification (20x, 40x) is recommended as well as an exact count of the stained cells (10% cutoff). In such cases, if there is any doubt, it is advisable to count tumor cells one field at a time (total number and positive cell number) and, if necessary, confirming the result by a colleague. Depending on the initial diagnostic situation, repeating a staining on the same or on a second tumor block (e.g. on a subsequent resection) should be considered.¹

1. Denkert, C., Lebeau, A., Schildhaus, H.U. et al. Neue Therapiemöglichkeiten beim metastasierten HER2-low-Mammakarzinom. Pathologie 43, 457–466 (2022). https://doi.org/10.1007/s00292-022-01124-x