MKI67 and lymphoma: The Ki-67 proliferation index usually ranges from 40% to 90% [4,53], and it has been suggested that highly proliferative tumors (Ki-67 > 90–95%) should be evaluated for MYC, BCL2, and BCL6 gene rearrangements, and further classified as ‘double-hit’ or ‘triple-hit lymphomas’ accordingly; nevertheless, both forms carry a poor prognosis despite aggressive chemotherapy, with frequent extranodal involvement [52,53].