Salivary duct carcinomas can be classified into luminal androgen receptor‐positive, HER2 and basal‐like phenotypes*

<jats:p>Di Palma S, Simpson R H W, Marchiò C, Skálová A, Ungari M, Sandison A, Whitaker S, Parry S & Reis‐Filho J S 
(2012) <jats:italic>Histopathology</jats:italic> <jats:bold>61,</jats:bold> 629–643</jats:p><jats:p><jats:bold>Salivary duct carcinomas can be classified into luminal androgen receptor‐positive, HER2 and basal‐like phenotypes</jats:bold></jats:p><jats:p><jats:bold>Aims: </jats:bold> The aim of this study was to devise a molecular classification for salivary duct carcinomas (SDCs) based on the similarities between SDCs and breast carcinomas and on characteristics of the microarray‐based gene expression profiling‐defined molecular subtypes of breast cancer.</jats:p><jats:p><jats:bold>Methods and results: </jats:bold> Forty‐two pure salivary duct carcinomas, 35 of which contained an <jats:italic>in‐situ</jats:italic> component as defined by histological review and/or immunohistochemical analysis, were stained with antibodies for oestrogen receptor (ER), progesterone receptor (PR), androgen receptor (AR), human epidermal growth factor receptor 2 (HER2), epidermal growth factor receptor (EGFR) and cytokeratin (CK) 5/6. Based on these markers, tumours were classified into HER2, luminal androgen receptor‐positive, basal‐like, luminal and indeterminate phenotype. Analysis revealed that 16.7%, 69%, 4.8%, 9.5% and 0% were of HER2, luminal androgen receptor‐positive, basal‐like, indeterminate and luminal phenotype, respectively. The <jats:italic>in‐situ</jats:italic> and invasive components displayed the same molecular subtype in all but one case.</jats:p><jats:p><jats:bold>Conclusions: </jats:bold> Salivary duct carcinomas can be classified into molecular subgroups approximately equivalent to those in the breast. We also report on the existence of a subgroup of bona fide pure salivary duct carcinomas that have a ‘basal‐like’ phenotype. Understanding the phenotypic complexity of SDCs may help to expedite the identification of novel therapeutic targets for these aggressive tumours.</jats:p>