<p>Describes and outlines the theoretical foundations of the OvaExpert system created by the author and his team</p><p>Demonstrates how the system helps physicians diagnose ovarian tumors using computational intelligence methods with particular focus on the problem of data incompleteness</p><p>Introduces basic information on medical diagnosis and the diagnosis of ovarian tumors</p><p>Discusses original algorithms based on the cardinalities of interval-valued fuzzy sets</p>