Cowdensyndrome(CS),anautosomaldominantdisorder,isoneofaspectrumofclinicaldisordersthathavebeenlinkedtogermlinemutationsinthephosphataseandtensinhomolog(PTEN)gene.Although70-80%ofpatientswithCShaveanidentifiablegermlinePTENmutation,theclinicaldiagnosispresentsmanychallengesbecauseofthephenotypicandgenotypicvariations.Inthepresentstudy,wesequencedtheexonsandthepromoterofPTENgene,mutationsandvariationsinthepromoterandexonswereidentified,andaPTENproteinexpressionnegativeregionwasdeterminedbyimmunohistochemistry(IHC).Inconclusion,anovelpromotermutationwefoundinPTENgenemayturnoffPTENproteinexpressionoccasionally,leadingtothedisorderofPTENanduntypicalCSmanifestations.