Polymorphous low-grade adenocarcinoma: the University of Pittsburgh experience

Abstract

Objective: To reappraise the clinical and histologic variables associated with a more aggressive outcome in polymorphous low-grade adenocarcinoma (PLGA).

Design: Retrospective cohort.

Setting: University hospital.

Patients: Twenty-four patients with PLGA treated from January 1, 1973, through December 31, 2005.

Main outcome measure: Analysis of clinical and pathologic variables in 30 biopsy or resection specimens from 24 patients.

Results: Only 4 PLGAs were not initially diagnosed as such. However, 8 non-PLGAs (thus excluded) were incorrectly diagnosed as PLGA. Most carcinomas (14 of 24 [58%]) were palatal. Recurrent carcinomas had a significantly higher mitotic rate (2.7 mitoses per 10 high-power fields) compared with primary tumors (1.2 mitoses per high-power fields, P = .046), and 3 of 7 (43%) recurrences showed progression to an intermediate-grade histologic type. No patient died of disease. Median disease-free survival was 12.8 years. Four of 24 patients (17%) had regional lymph node metastases, 3 with carcinomas of the base of the tongue. One PLGA metastasized to the subcutaneous tissue of the face, orbit, and lungs at 19.6 years. An extrapalatal site was the only significant determinant of disease-free survival (P = .03).

Conclusions: Diagnosis of PLGA remains a challenge. Extrapalatal carcinomas appear to behave in a more aggressive fashion than those of the palate, and cancer arising from the base of the tongue frequently metastasizes to the cervical lymph nodes, suggesting a role for neck dissection in these patients. Recurrent cancers show evidence of histologic progression, justifying an aggressive approach to achieving initial complete excision.