Diversity of collagen expression in the pleomorphic adenoma of the parotid gland.

The high diversity of collagen expression and its qualitative and quantitative aspects are demonstrated in pleomorphic adenoma using electron microscopy and specific histochemical methods. Great variability was observed in the amount, distribution and characteristics of the collagen found in the various types of tissue normally present in this tumour. Both deficient polymerization and hyperpolymerization of collagen and the occurrence of desmoplasia were observed. Evidence is presented to suggest a role for localized collagenolysis in the invasiveness of this neoplasia.