Methods and compositions for diagnosis and/or analysis of a condition in a mammal are disclosed in which RNA from microvesicles is enriched and differentiated to so obtain a result that is indicative of the condition of tissue or organ from which the microvesicle originated. In especially preferred embodiments, the condition is a neoplastic disease of a human and can be identified and staged by differential analysis of one or more distinct RNAs, optionally together with identification and analysis of a non-RNA component of the microvesicle.