[Reproducibility of nuclear grade in breast neoplasm. A multicenter experience]

Nuclear grade is considered a valuable prognostic factor in mammary carcinomas. Since the histological diagnosis of most of these tumors is made by "non expert" pathologists, it was considered interesting to find out the reproducibility of general pathologists to define the nuclear grade. In order to do this, a series of 15 mammary carcinomas, 10 of them randomly selected and 5 because they were considered difficult to classify for nuclear grade, were examined separately by 10 general pathologists. In a first round of observation, each one of them graded the cases according to their own criteria as used routinely, and for a second round they followed a written guide. An analysis of variance was applied to the data and no significant differences were found between observers, neither in the randomly selected cases nor in the total series. The written guide, surprisingly, instead of lowering the differences, increased them. Analysis of the individual performance of observers showed two of them having a great variation between both rounds of observation, and this was considered to influence the results of the whole group. Interobserver performance to discriminate high grade tumors (G3) from the rest, showed a good correlation in all the participants. These results allow us to conclude that in this series, examined by general pathologists, an acceptable reproducibility was observed, specially when high risk tumors were being identified.