Phenotypes in canalicular adenoma of human minor salivary glands reflect the interplay of altered secretory product, absent neuro-effector relationships and the diversity of the microenvironment

Aims: Uncertainty about the factors influencing phenotypes in salivary cana licular adenoma prompted the present investigation. Methods and results: Specimens of canalicular adenoma from 15 patients were examined with the use of histology, histochemistry for protein, mucosubsta nces and pigments, nerve staining and immunocytochemistry for cytoskeleton components. The tumours consisted largely of simple cells lining tubules th at were occasionally cystic or branching and budding, and were set in loose , vascular and often haemorrhagic stroma. Other phenotypes recognized were mucous cells, apocrine-like cells, pigmented cells, microliths and stromal macrophages, detected in 26.6%, 20%, 33.3%, 20% and 53.3% of the patients, respectively. Simple cells showed moderate levels of -SH groups and strong immunoreactivity for 'simple' epithelial phenotype cytokeratin. The simple cells lining cystic tubules showed additional immunoreactivity for 'stratif ied' epithelial phenotype cytokeratin, possibly an adaptation to mechanical pressure. Lumina showed variable levels of neutral and carboxylated glycop roteins, and chondroitin sulphate. Stroma showed high levels of chondroitin sulphate and hyaluronic acid. Mucous cells showed high levels of -SS- grou ps and nonsulphated glycoproteins. Apocrine-like cells contained lipofuscin . Pigmented cells contained haemosiderin, possibly a consequence of localiz ed iron overload. Microliths contained mucosubstances. Macrophages often co ntained lipofuscin. No nerves were found in relation to the tumours. Conclusions: The results suggest that, contrary to popular belief, phenotyp es in canalicular adenoma do not reflect histogenetic concepts but rather m ay derive from the interplay between an altered secretory product, consisti ng of glycosaminoglycan and an immature form of glycoprotein, the lack of n euro-effector relationships and the different microenvironments throughout the tumour.