Diagnostic Significance of Ki67 Staining Pattern in Benign Peripheral Nerve Sheath Tumors: An Additional Diagnostic Tool

Introduction. Benign peripheral nerve sheath tumors involve mainly neurofibromas, schwannomas, and their variants. Ki67 is a widely used immunohistochemical marker that predicts the proliferation rate of tumors including the nerve sheath-derived neoplasms and it is helpful to differentiate them from their malignant counterparts. However, Ki67 score is not used in distinction of the benign peripheral nerve sheath tumors types from each other. Our aim is to contribute to the literature by identifying the hypothesized specific Ki67 staining patterns of benign peripheral nerve sheath tumors. Methods. Fifty-three tumors (distributed as follows: 26 schwannomas, 24 neurofibromas, and 3 hybrid schwannoma-neurofibroma tumors) from 49 patients were included in the study. Two researchers analyzed the slides independently. Tumors were classified according to their Ki67 staining patterns in 3 different groups: zonal (Z-Ki67), focal zonal or mixed (M-Ki67), and scattered Ki67 (S-Ki67). Results. There was a significant correlation among the types of benign peripheral nerve sheath tumor and the Ki67 staining patterns ( P < .01). Level of inter-rater reliability was calculated as good (>0.7) and excellent (>0.8) according to 2 different calculations of kappa score. Conclusions. In conclusion, our study demonstrates that the Ki67 staining pattern may be used as an additional diagnostic tool in the diagnosis of benign peripheral nerve sheath tumors.