MKI67 and neoplasm: After surgical resection, the histopathological analysis (Fig 3) showed a highly heterogeneous tumor: benign areas were contiguous with the malignant ones (with a maximum tumor mitotic rate of eight mitoses per 10 HPF, a high Ki67 index of about 50%, and focal S100 immunohistochemical staining) and associated with a dense peritumoral lymphocytic infiltrate (stromal reaction).