Four cases of polymorphous low-grade adenocarcinoma.

Since its histologic recognition by the World Health Organization in 1990, polymorphous low-grade adenocarcinoma (PLGA) is now regarded as the second most common salivary gland tumour after mucoepidermoid carcinoma. Distinguishing it from high-grade tumours such as adenoid cystic carcinoma or carcinoma arising within a pre-existing pleomorphic adenoma is important, as PLGA may usually be treated by local excision alone. Any evidence of incomplete marginal clearance, perineural and perivascular spread, and lymph-node involvement is treated with a course of radiotherapy. Follow-up should be for life, and as reported in this series, long-term survival rates are very good, one of our patients surviving for 11 years. The importance of reporting these cases is emphasized.