MKI67 and neoplasm: When the malignant transformation of HAS occurs, the vascular lumens anastomose with each other and form a sieve mesh, with pseudo-papillae and solid areas, heterogeneous proliferation of tumor cells, spindle/or epithelioid morphology, heterogeneous distribution of chromatin, enlarged nuclei, and pathologic karyotypes, with strong diffuse positivity of P53 and P16, increased Ki-67 proliferative activity, suggest malignant transformation of HAS.