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Six cases of salivary duct adenocarcinoma are presented. All had a history of a rapidly enlarging mass in the parotid gland with involvement of the facial nerve. The histopathological appearance was distinctive, each case showing an invasive tumour resembling ductal carcinoma of the breast, often with areas of comedo necrosis. Five patients died within 26 months, and the one long-term survivor (68 months) has widespread metastatic disease. These findings are similar to cases which have previously been described, but the tumour has not been widely reported, particularly in Britain. We feel that salivary duct adenocarcinoma is a distinct clinicopathological entity and, as its histological appearance is usually unmistakable, we believe it deserves wider recognition.

The nature of cell-associated carbohydrates in the human intestine that may mediate transepithelial transport of bacterial and dietary lectins and their processing by the lymphoid cells of Peyer's patches is not known. Because the cell surface carbohydrate receptors for lectins may vary in different species, the glycoconjugates of human and mouse follicle-associated epithelium and gut-associated lymphoid tissue were compared. A panel of 27, mainly recently isolated, lectins were used to identify glycoconjugate expression in M-cells, enterocytes, goblet cells, lymphocytes and macrophages in mouse and human intestine. Mouse M-cells were exclusively labelled by fucose-specific lectins but in human follicle-associated epithelium no distinct M-cell staining pattern was observed. In the human Peyer's patches, Bryonia dioica lectin bound selectively to paracortical T-lymphocytes and Chelidonium majus lectin to germinal centre B-cells. Certain mannose-specific lectins (Galanthus nivalis, Hippeastrum hybrid) stained the tingible body macrophages in the germinal centre of human Peyer's patches but labelled the macrophages in the paracortical T-cell region of the mouse. The results indicate distinct differences in glycosylation between mouse and human Peyer's patches and their associated lymphoid cells. When considering cell surface glycoconjugates as target molecules for the gut immune system, care has to be taken to choose the appropriate lectin for each species.

Two cases of carcinoma of the minor salivary glands are presented in which most cells had clear cytoplasm. Both patients had clinical histories in excess of 10 years and, in the one case with adequate follow-up, no recurrence had occurred after a further 11 years. Both tumours were locally invasive. The clear cells contained small amounts of glycogen, but no intracytoplasmic mucin. Immunohistochemical and ultrastructural studies showed epithelial features, with no evidence of myoepithelial differentiation. These tumours were very similar to the small number of previously reported cases, which were all considered to be low-grade carcinomas. Amongst the differential diagnoses, the most important is metastatic clear cell carcinoma of the kidney and this can only be confidently excluded clinically or by the use of imaging techniques. In summary, we consider intraoral clear cell carcinoma to be a distinct tumour of low malignant potential.

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