I will start a systematic literature review of my research topic. Before embarking on this venture, I searched for already existing systematic reviews, mapping or survey papers but I have not found any literature review or survey that directly relates to my topic although I have found many surveys which are related to one aspect of my research area but not whole. (e.g. my topic is Methods of Y in Z. I have found existing reviews related to Methods of Y but they do not cover Z.)
I have been taking notes from these papers as I read them. Now my question is: What would be the value of these existing reviews in my literature review? Can I refer these to justify my review with the fact that they do not cover my whole research area? or refer some interesting points raised by existing reviews in my review?