Some databases have features that help you search for case study publications. For example, MEDLINE and CINAHL include some Subject Headings or Publication Types that help retrieve case study publications.
Case study research is defined as a qualitative approach in which the investigator explores a real-life, contemporary bounded system (a case) or multiple bound systems (cases) over time, through detailed, in-depth data collection involving multiple sources of information, and reports a case description and case themes. The unit of analysis in the case study might be multiple cases (a multisite study) or a single case (a within-site case study).
Creswell JW. Research design: qualitative, quantitative and mixed methods approaches. 4th ed. Thousand Oaks, CA: SAGE; 2014.