Molecular and biomarker analyses of salivary duct carcinomas: Comparison with mammary duct carcinoma

Salivary duct carcinoma (SDC) is a rare high-grade aggressive neoplasm that manifests close histologic features with invasive ductal carcinoma of the breast (IDC). In contrast to SDC, extensive molecular studies have been per formed on IDC and led to the identification of certain biological markers. To investigate the underlying molecular and biologic characteristics of SDC , we performed molecular analyses using microsatellite markers on chromosom al arms 6q, 16q, 17p, and 17q, DNA flow cytometry and immunohistochemical s taining for androgen receptor (AR) and p53 expression on 28 examples of the se tumors in comparison to 24 IDC cases. Our results show that generally si milar allelic alterations, elevated p53 and androgen receptor expressions, and high frequency of DNA aneuploidy are manifested in both SDCs and IDCs. Differences at certain markers on 6q, 17p and 17q chromosomal loci, however , were observed between the two entities. Certain loci on 6q were more freq uently altered in SDC than IDC which loci on chromosomes 17p and q arms wer e more seen in IDCs than SDCs. The majority of SDCs had high AR expression while most of IDCs were AR negative. Our study indicates that: i) SDC may s hare some genetic alterations with IDC, ii) high AR expression in SDC may p lay a role in tumor progression, and iii) p53 overexpression and DNA aneupl oidy in both entities reflect their aggressive behavior.