Two is the minimum, but the value of your case series depends on a) the novelty of the cases and b) your ability to characterise the phenomenon. If the two cases differ significantly then a complete description is going to require more cases to capture the variability.
Two is the minimum, but the value of your case series depends on a) the novelty of the cases and b) your ability to characterise the phenomenon. If the two cases differ significantly then a complete description is going to require more cases to capture the variability.
The diference between case reports and case series is not well defined. Case series is a descriptive study that follows a group of patients who have a similar diagnosis and may generate hypotheses that will be useful in designing further studies, so two is the minimum, theoretically.