Background: Medical decision-making is complex and involves a variety of decision criteria, many of which are universally recognised. However, decision-making analyses have demonstrated that certain decision criteria are not used uniformly among clinicians. Aim: We describe decision criteria, which for various contexts are only used by a minority of decision makers. For these, we introduce and define the term "insular criteria". Methods: 19 studies analysing clinical decision-making based on decision trees were included in our study. All studies were screened for decisionmaking criteria that were mentioned by less than three local decision makers in studies involving 8-26 participants. Results: 14 out of the 19 included studies reported insular criteria. We identified 42 individual insular criteria. They could be intuitively allocated to seven major groups, these were: comorbidities, treatment, patients' characteristics/preferences, caretaker, scores, laboratory and tumour properties/ staging. Conclusion: Insular criteria are commonly used in clinical decision-making, yet, the individual decision makers may not be aware of them. With this analysis, we demonstrate the existence of insular criteria and their variety. In daily practice and clinical studies, awareness of insular criteria is important.