MKI67 and neoplasm with perivascular epithelioid cell differentiation: Infiltrative growth or edges, marked hypercellularity, and marked nuclear pleomorphism/atypia may be secondary features suggesting aggressive behavior or malignancy.[7,33,34,35] Most reported malignant PEComas contained necrotic areas, and many revealed high mitotic index.[1,8,12,15,16,19,37] The risk of recurrence and metastasis risk is low if the Ki-67 marker index is less than 1% of PEC tumors.[34] We noted that Ki-67 labeling of 5% of neoplastic cells was observed in PEComas in the colon and rectum that behaved aggressively in Table 1.