This letter evaluates the study by Milev and Ivanov (2025) comparing MIB1 and SP6 antibodies for Ki-67 assessment in breast carcinoma and outlines key methodological limitations that weaken the reliability of their conclusions. The use of a single, non blinded pathologist without interobserver or intraobserver reproducibility assessment raises concerns about scoring subjectivity. The absence of formal agreement analyses, such as Bland Altman plots, further limits confidence in the reported concordance between the two clones. Additionally, the study lacks a predefined primary endpoint, sample size justification, and power calculation, reducing its interpretive strength. Addressing these issues would enhance reproducibility, analytical validity, and the translational relevance of Ki-67 evaluation.