Polymorphous low-grade adenocarcinoma of the palate: report of cases

Polymorphous low-grade adenocarcinoma (PLGA) is a rare tumor that mostly affects minor salivary glands. The purpose of this study is to report six new cases followed-up during a long period. We also review the literature concerning clinical, histological and immunohistochemical features, as well as the proper management.

Malignant tumors of the salivary glands diagnosed in our department from 1990 to 1999 were reviewed. A total of 66 cases were registered. Six of these cases were diagnosed as PLGA. All cases satisfied the histopathological criteria for this entity, and at least 3 years follow-up was available.

In the six cases the primary location was the mucosa of the palate. Hard palate was affected in 83.3% of the cases. There were no cases of extraoral PLGA in our series. Tumors were ulcerated in a 16.6% of the cases, and exofitic in the other 86.4%. Histologically, it was observed a tumoral proliferation of round clusters of uniform cells with round-to-oval clear nuclei and small nucleoli. All the cases underwent surgical management with local excision with surgical margins, five of them with bone extirpation associated. No recurrence was observed in four cases, whereas the remaining two cases showed recurrence in the follow-up. In one of the patients, lococervical recurrence appeared 12 months after the surgery, and this patient died after a few months. The remaining patients have been followed-up for 11, 7, 4 and 3 years postoperatively, with no evidence of recurrence.

Our results for a long follow-up period support the idea for a low grade of malignancy and good prognosis of this tumor, but the appearance of recurrences many years after the surgery must induce us to be very careful and systematic with the follow-up.