<p>Disclosed is a method for amplifying/detecting cytokeratin-19 mRNA in an RNA amplification process. The RNA amplification process comprises the steps of: producing double-stranded DNA containing a promoter sequence with a reverse transcriptase using an oligonucleotide combination consisting of a first primer having a sequence homologous to a part of cytokeratin-19 mRNA and a second primer having a sequence complementary to the first primer (provided that either the first primer or the second primer has the promoter sequence added to the 5'-terminal thereof); producing an RNA transcript with an RNA polymerase using the double-stranded DNA as a template; and further producing the double-stranded DNA using the RNA transcript as a template for the DNA synthesis with the reverse transcriptase. The method comprises measuring the quantity of the amplified RNA product over time using an oligonucleotide probe that is so designed as to undergo a change in signal properties upon the formation of a complementary double strand between the oligonucleotide probe and the amplified RNA.</p>
