Abstract: In certain examples, computer-implemented methods involve assessing patient diagnosis utilizing RNA expression profiles. As may be implemented in accordance with one or more aspects characterized herein, a landscape of RNA expression profiles may be generated from a plurality of patients having a set of common medical attributes. An RNA expression profile is obtained for a target patient having the medical attributes, and a plurality of nearest neighbor RNA expression profiles are identified from the landscape of RNA expression profiles, based on the target patient's RNA expression profile. A diagnosis for the target patient is provided, or identification of certain ones of the patients is identified, based on known characteristics of the plurality of patients corresponding to the identified nearest neighbor RNA expression profiles.