I thank the Editor for giving me an opportunity to write a commentary to the article written by Dr. Chen. This study mainly is the research of the correlation between CXCR4 expression and brain-specific metastasis in non-small cell lung cancer. The method of tissue analysis seems straightforward and clear cut, and the results were statistically significant. Also, there is no doubt that the final data contribute to the future medicine. However, there are two points that the authors have to strengthen.

  1. (1)

    The major drawback of the article is the method of tissue analysis: immunohistochemistry staining was the only one that they used. As we know, immunohistochemistry staining is supposed to be a subjective method of evaluation, even by two independent pathologists. We cannot preclude the bias during the examination. On the contrary, Western blot or RT-PCR, which gives objective quantitative study of RNA and protein expression, strongly supports the results. They are indispensable in the modern scientific research in this field.

  2. (2)

    When we carefully looked into the scoring system, there was overlapping of the grading of proportion of stained tumor cells, i.e., 0 = 0–5% and 1 = 5–10%. If it is 5%, what grade should it belong to? Also, the detail tablet of the scoring system should be described and shown.

This is an important preliminary work, but until we have RT-PCR data or Western blot data, we cannot view this as definitive proof!