Polymorphous low grade adenocarcinoma: a clinicopathologic study of 164 cases

Polymorphous low grade adenocarcinomas (PLGA) are minor salivary gland neoplasms with a predilection for intraoral sites.

One hundred sixty-four cases of PLGA diagnosed between 1970-1994 were retrieved from the files of the Armed Forces Institute of Pathology, Washington, DC. Histologic features were reviewed, immunohistochemical studies and prognostic markers were performed, and patient follow-up was obtained. The data were analyzed statistically.

The patients included 109 women and 55 men, ages 23-94 years (average, 57.6 years). The patients usually presented clinically with a palatal mass that ranged in size from 0.4-6 cm (average, 2.2 cm). The tumors were infiltrative and characterized by a polymorphous growth pattern, with individual tumors demonstrating multiple patterns, including solid, ductotubular, cribriform, trabecular, and single file growth. Neurotropism was identified frequently. The neoplastic cells were isomorphic with vesicular nuclei. Mitotic activity was inconspicuous. At an average of 115.4 months after presentation, approximately 97.6% of all patients were either alive or had died without evidence of recurrent disease after treatment with surgical excision only. Four patients had evidence of disease at last follow-up; three had died with evidence of tumor, and one patient was alive with tumor.

PLGA is a neoplasm of minor salivary gland origin that must be separated from adenoid cystic carcinoma and benign mixed tumor for therapeutic and prognostic considerations. Conservative but complete surgical excision is the treatment of choice for these slow-growing tumors with a low proliferation index; adjuvant therapy does not appear to alter the prognosis.