[Malignant mixed tumors of the parotid gland: a review of the Department of Otolaryngology Medical University of Warsaw experience]

Abstract

Objectives: Pleomorphic adenoma (PA), or benign mixed tumor, is the most common salivary gland neoplasm. One of the factors influencing the management strategy in parotid PA is the risk of malignant transformation of this tumor. The objective of this study was the clinical and pathological analysis of malignant mixed tumors treated surgically at the Department of Otolaryngology, Medical University of Warsaw.

Materials and methods: Retrospectively analysed clinical material included 12 patients with malignant mixed tumors selected from the group of 423 patients who underwent surgical treatment for parotid pleomorphic adenoma at the Department of Otolaryngology, Medical University of Warsaw, between January 1988 and June 2010. There were 7 women and 5 men; age ranged from 39 to 67 years, with a mean of 56 years. The following parameters were analysed: demographic data, symptoms and disease duration, results of diagnostic tests, intraoperative data, results of histopathological examination, and adjunctive therapy. Four patients with a follow-up shorter than 5 years were excluded from the analysis of treatment results.

Results: A group of 12 patients with malignant mixed tumours included 10 (83.3%) cases of a primary tumor and 2 (16.7%) cases of a recurrent tumor. In the complete study sample (n=423), patients with malignant mixed tumor comprised: 2.8% of all patients, 2.5% of patients with primary PA and 5.1% of patients with recurrent PA. Patients with malignant mixed tumor were significantly older than patients with benign PA (an average patient age was 56.0 and 43.2 years, respectively p<0.001). 83.3% (n=10) patients were older than 50 years. An average disease duration was longer in patients with malignant tumors. Considering all data from preoperative patient assessment (medical history, physical examination, FNAB, imaging studies), a preliminary diagnosis of malignant disease was made in 6 (50%) patients. All patients were treated surgically and 10 also had radiation therapy. The group of patients (n=8), subjected to evaluation of treatment results, included three patients with non-invasive carcinoma and five patients with invasive carcinoma. All patients with non-invasive carcinoma were free from disease symptoms during the follow-up of 9 to 21 years after the treatment. Five-year survival was 80% (4 of 5 patients) in a group of patients with invasive carcinoma. The rate of death for the underlying disease was the same (80%). An overall 5-year survival in patients with malignant mixed tumor was 87.5%.

Conclusions: 1. Malignant transformation of pleomorphic adenoma more frequently occurs in recurrent tumors and in older patients. 2. Uncharacteristic clinical picture of malignant mixed tumors allows to make an accurate initial diagnosis only in half of the patients. 3. Extracapsular cancer invasion is a vital prognostic factor. Overall 5-year survival for invasive and noninvasive carcinoma was 80 % and 100 % respectively.