Pathology of the Head and Neck

158 S. Di Palma · R.H.W. Simpson · A. Skalova · I. Leivo5the history will usually be that of rapid growth in a longstandingsalivary nodule.Microscopy shows a biphasic tumour composed ofepithelial and mesenchymal elements. The former isgenerally a poorly differentiated (adeno)carcinoma,but salivary duct carcinoma is increasingly reported(Fig. 5.52) [49, 50]. The other component is usuallya chondrosarcoma, but osteogenic sarcoma, fibrosarcoma,malignant fibrous histiocytoma, pleomorphicrhabdomyosarcoma and osteoclast-type giant cellneoplasms [214, 224] have also been described.Epithelial markers are usually detected in the epithelialcomponent, which may or may not also be expressedin the sarcomatous component. Positive stainingfor epithelial markers has been used as proof of thefact that CS are carcinomas showing divergent differentiationand as an indication of their monoclonal origin.However, keratin staining can be negative castingdoubt onto the monoclonal-carcinomatous nature ofthe whole tumour. Molecular studies have been helpfulin clarifying this issue. In analogous neoplasmsin other organs such as breast, uterus and in salivaryglands, molecular studies have demonstrated that carcinomatousand sarcomatous components have similargenetic profiles. Moreover, in a subset of CS withosteoclastic-type giant cells, Tse et al. [224] found mutationof the same allele on chromosome 17p13, whichis a known mutation of salivary duct carcinoma. Thisindicates that carcinosarcoma are in fact carcinomasof high-grade malignancy and should be treated assuch. HER-2 overexpression on immunohistochemistryis also seen in the salivary duct component of CS.The meaning of this information has still not beenclarified [57].5.9.11.3 MetastasisingPleomorphic AdenomaICD-O:8940/0This tumour is histologically indistinguishable frombenign PA, yet it metastasises widely to sites includinglymph nodes, bone, lung and kidney, and can kill thepatient [232]. Whereas the WHO revised classificationlists metastasising pleomorphic adenoma (MPA)as one entity in the MMT category of [171], it differsbecause it remains histologically “benign” in the primarysite, local recurrences, and metastatic deposits[56, 232].It is a rare tumour with fewer than 100 reported casesso far. Despite this, MPA has a clear-cut clinicopathologicalprofile: the reported cases shared several similarities,such as long time intervals (up to 50 years) betweenthe primary tumour and metastases, and simultaneous,usually multiple, local recurrences and distantmetastases [232]. Although the morphology of both isalmost identical, the recurrences seem to play an importantrole in the genesis of systemic spread. This suggeststhat surgical manipulation may favour vascularimplantation or invasion eventually leading to metastases,but in many cases of MPA it was not possible histologicallyto demonstrate actual vascular permeation[56, 232].5.9.12 Sebaceous CarcinomaICD-O:8410/3Although sebaceous glands are common in the oral mucosa(Fordyce granules), sebaceous neoplasms of the salivaryglands are rare. Most sebaceous carcinomas havearisen in the parotid [62], possibly from pluripotent ductcells [219]. The sex incidence is equal, and the meanage is 69 years (range 17–93). Macroscopically, they arepartly encapsulated and vary in size from 6 to 85 mmacross the greatest diameter. Microscopy shows invasiveislands, duct-like structures and sheets of tumourcells, which may be sebaceous, squamous or basaloid;intracellular mucin may be found [12]. Sebaceous cellsare present in varying numbers, and typically comprisefoamy cytoplasm and a single vesicular nucleus witha prominent nucleolus. Areas of necrosis are frequent[85]. The tumour cells react with cytokeratin and EMA,but not with S-100 protein or actin [219]. The behaviouris intermediate to high-grade, and recurrences, metastasesand death due to disease have all been reported.Three cases of sebaceous lymphadenocarcinoma havebeen described, representing malignant transformationof sebaceous lymphadenoma. One of the patients diedbecause of the tumour [62].5.9.13 Lymphoepithelial CarcinomaICD-O:8082/3The WHO revised classification includes this tumourunder undifferentiated carcinomas [171], but it is a genuineclinicopathological entity and can be consideredseparately.Lymphoepithelial carcinoma is extremely rare exceptin Eskimos (Inuit) and in Southern China. Themedian age is 40 years (range 10–86), and it is slightlycommoner in females [62]; familial clusters have beenidentified amongst patients from Greenland [1]. Theparotid is involved in 80% of cases, with the rest occurringin the submandibular glands. Forty per cent of patientshave lymph node metastases at the time of presentation.A few examples have been described in associationwith lymphoepithelial sialadenitis [121], but amuch more important association is with Epstein-Barr