MKI67 and neoplasm: AciCC with high-grade transformation is considered to be more aggressive and predictive of recurrence and distant metastases; despite a histologic grading system is still lacking, frequent mitosis, ki-67 proliferation > 5%, perineural and vascular invasion, infiltration and tumour necrosis are regarded as high-grade features, explaining the aggressive behaviour of these dedifferentiated tumours [21, 22].