Pathology of the Head and Neck

Major and Minor Salivary Glands Chapter 5 155Fig. 5.48. Salivary duct carcinoma: invasive irregular ducts andcribriform structures strongly resemble ductal carcinoma of thebreastFig. 5.49. Salivary duct carcinoma, mucin-rich variant. This iscomposed of a mixture of usual-type salivary duct carcinoma andlakes of mucinous adenocarcinomacarcinoma [142]. Some studies have shown SDCs to expressprostate specific antigen (PSA) or acid phosphatase[110, 120], but another failed to confirm this [185] andsimilarly, only 1 out of 40 cases in a Mayo Clinic serieswas PSA-positive [115]. More recently cases of SDC showingpositive staining for HER-2/neu (c-erbB-2) protein onimmunohistochemistry have been published [202], andthe gene amplification has been demonstrated with FISHanalysis [204].Several rare morphological variants of SDC havebeen described, including cribriform [23], micropapillary[147], sarcomatoid [96], mucin-rich [190] and oncocytic(Figs. 5.49, 5.50) [184]. So-called low grade salivaryduct carcinoma [46] is probably a separate entity(see below).The differential diagnoses of SDC are high-grademucoepidermoid carcinoma, oncocytic carcinoma andsome metastases. The diagnosis of mucoepidermoidcarcinoma requires the presence of squamous-like cells,mucus-producing cells and cells of intermediate type,and there is no expression of androgen receptors. Manysalivary oncocytic carcinomas probably demonstrateother types of malignancy (including SDC) with plentifuloncocytic cells, but a true oncocytic carcinoma lacksany features of SDC and is AR-negative. At present, neitherof these two differential diagnoses is clinically criticalsince the prognosis is similar. However, it is importantto identify metastatic carcinoma, particularly fromthe prostate or breast. In most cases, metastases will beobvious from clinical investigation and imaging studies,but the usual immunoprofile of these tumours is different:prostatic carcinomas tend to be AR+, ER−, PSA+,CK 7+; breast carcinoma tend to be usually AR−, oftenER +, PSA−, CK 7+; SDC is AR+, ER−, usually PSA−, andCK 7+.Fig. 5.50. Salivary duct carcinoma with oncocytic differentiation.The cells have ample granular cytoplasm with vesicular nucleiand prominent nucleoli. A clear distinction between oncocyticsalivary duct carcinoma and true oncocytic carcinoma may notbe possible, as they may not be separate entitiesThe prognosis for SDC is poor, and most series haveshown that more than 70% of patients die of disease,usually within 3 years. Nevertheless, Grenko et al. [86]alluded to a minority (about 25–30%) who do well, buttheir study was unable to identify any particular featuresof this group. Amongst possible prognostic indicators,tumour size is probably important, with lesions