pathology
Last reviewed 01/2018
Pleomorphic adenomas are derived from salivary gland epithelium. Macroscopically, they appear as a firm, mobile, smooth and lobulated tumour lying within a false capsule of compressed salivary tissue. Microscopically, they show varying degrees of differentiation. Hence, the name pleomorphic adenoma.
Columns and islands of neoplastic epithelial cells are surrounded by myoepithelial cells and separated by a myxomatous connective tissue stroma, often containing areas resembling immature cartilage. This led early pathologists to believe that the tumour contained neoplastic tissue of both epithelial and connective tissue origin, resulting in the misleading name of mixed salivary tumour. Some have no myxomatous tissue and are described as monomorphic variants.
Often, the tumour has 'amoeboid processes' which may be left behind during removal causing later recurrence.