MKI67 and malignant peripheral nerve sheath tumor: The mitotic index (Ki-67) is a useful indicator of a tumor’s benign or malignant potential.[15] Benign schwannomas typically have low Ki-67 expression levels (0–6%, median 4%), while malignant schwannomas tend to have higher levels (12–45%, median 25%).[16] A Ki-67 index >20% is highly predictive of malignant peripheral schwannomas.[17] For patients with benign schwannomas, surgical excision can achieve excellent outcomes with a good prognosis.[4,18] In contrast, malignant schwannomas require multimodal treatment, primarily based on surgery.[19]