1. A method for detecting mammalian RNA having a nucleotide sequence other than an oncogene sequence in plasma or serum from a human or animal, the method comprising the steps of: a) extracting total extracellular RNA from plasma or serum from a human or animal, wherein a fraction of said extracted extracellular RNA comprises a nucleotide sequence other than an oncogene sequence; b) amplifying to produce an amplified fragment or signal amplifying to produce an amplified signal of said fraction of the extracted extracellular RNA or cDNA produced therefrom, wherein amplification is performed either qualitatively or quantitatively using primers or probes specific for a portion of the nucleic acid sequence of said extracted extracellular non-oncogene RNA or cDNA thereof; c) detecting the amplified fragment or amplified signal produced from the extracted extracellular RNA or cDNA thereof.