Discriminating between micrometastases and isolated tumor cells in a regional and institutional setting

The reproducibility of diagnosing isolated tumor cells (ITC) and micrometastases has been recently tested by expert breast pathologists, but might be different in a community setting. Digital images of 50 cases of low volume nodal involvement were circulated among pathologists from the Piedmont region (Italy) and from the Helios Medical Center in Berlin. Participants were asked to categorize the lesions into micrometastasis, ITC or others. The test was performed on the basis of a previous consensus statement. Kappa statistics were used for the assessment of interobserver variability. The kappa values for the consistency of categorizing cases were 0.47 and 0.57 for the regional and the institutional tests, respectively. Our study suggests that the reproducibility of diagnosing micrometastases and ITC in a community setting may reach that of experts, but is in the moderate range, and this may interfere with studies trying to solve the prognostic significance of these diagnostic categories.