Papillary cystadenoma and cystadenocarcinoma of salivary glands: two unusual entities.

Cystadenoma and cystadenocarcinoma are rare salivary gland tumours histologically characterized by prominent cystic and frequently papillary growth. We present two cases of cystadenoma of a minor salivary gland (upper lip) and parotid cystadenocarcinoma respectively, captured between 834 salivary gland tumors studied in our hospital from 1980 to 2004. The authors review the clinical, histological, and biological features of these two unusual tumours, and differential diagnosis with other salivary glands neoplasms. Both entities usually reveal papillary proliferation of the epithelial lining and are composed of cells that possess bland cytomorphologic features. Differentiation of tumour types depends largely on the identification of actual infiltration of salivary gland parenchyma or surrounding connective tissue by either cystic or solid epithelium in cystadenocarcinomas. Step sections of a borderline tumour may yield unequivocal evidence of invasion. The authors discuss the problematic diagnosis between these rare neoplasms and with other tumours and compare histological findings of these two entities.