ADAMS (a desintegrin and metalloprotease) are transmembrane multifunctional glycoproteins, involved in cell growth, differentiation, motility, cell signaling and respectively, tumor growth, progression and spread. Our purpose was to confirm the up-regulation of ADAM17 (tumor growth factor alpha converting enzyme) gene in benign and malignant breast tumors and, knowing that the expression of a gene at transcriptional level is not always correlated with the protein expression, we aimed also to compare the mRNA expression of ADAM17 gene with the expression of ADAM17 protein. Expression of ADAM17 transcript was analyzed using quantitative reverse-transcription polymerase chain reaction and the protein expression was evaluated using immunohistochemistry in breast tumors and corresponding non-neoplastic breast specimens from 63 patients. Significantly elevated amounts of ADAM17 transcripts were found in malignant breast cells compared with normal adjacent breast tissue. ADAM17 was also up-regulated in benign versus non-tumor samples and in malignant versus benign tumors but, in these cases the difference was not statistically significant. The expression of ADAM17 protein was immunohistochemically confirmed in all investigated carcinomas. A moderate immunoexpression was noticed also in the benign tumors, whereas normal adjacent acini displayed a low expression. Our study confers further evidence that ADAM17 is implicated in breast cancers tumorigenesis and progression and could represent an interesting marker and therapeutic target for breast cancer.