Studiu retrospectiv asupra tumorilor de glandă parotidă

Introduction

The salivary glands, either major or minor, can host tumors, benign or malignant, usually of epithelial nature. Minor or accessory salivary glands although very numerous (450 to 750) can rarely develop a tumor mass. The parotid glands are the most common site for tumor pathology. Most of the tumors are benign. Malignant gland tumors comprise 3% of head and neck cancers and 3% of all malignant processes(1). The pleomorphic adenoma is the most common salivary gland tumor and approximately 80% is found in the parotid gland(2). The second place is occupied by Warthin tumor which is found exclusively in the parotid glands. The mucoepidermoid carcinoma is the most encountered malignant tumor of the salivary glands, usually involving the minor salivary glands; up to 50% of all malignant accessory glands tumors(3).

Material and method

A group of 56 patients diagnosed with parotid tumors during 2011-2015 was analyzed. 57% (no=32) were male. The age span was from 8 to 78 years old, with the median being 54 years old. After a careful clinical evaluation, all the patients were subjected to MRI or CT head and neck examinations. After paraclinical investigation the patients were subjected to parotid gland surgery in general anesthesia. The surgical procedure was partial or total parotidectomy with or without preserving the facial trunk and branches. If there were clinical and imagistic signs of malignancy with node involvement, a modified neck dissection was performed. After 3 weeks, a histopathological examination was delivered by the pathological laboratory. In malignant cases patients underwent radiotherapy after surgical treatment. The median follow-up period was 35.4 months. No local relapse was noted during this period of time.

Results

The benign pathology represented 72% of the cases. 85% of the benign tumors were epithelial tumors. There were only 2 pediatric patients: an 8-year-old girl and a 9-year-old boy, both diagnosed with lymphangiomas. The most common benign tumor was the pleomorphic adenoma (70%) and Warthin tumor (15%). There was bilateral involvement in 3% of the cases (2 patients), all diagnosed with Warthin tumor. Non-epithelial benign tumors represented 15% of the benign tumors. There were 2 lymphangiomas, 2 lipomas, 1 neurinoma and 1 hemagiopericytoma. There was one case of giant Warthin tumor involving the parapharyngeal space. 
The adenoid cystic carcinoma was the most common malignant tumor in the group (31% and 9% of all cases, no=5). The mucoepidermoid carcinoma was found in 25% of the malignant cases and in 7% of all cases (4 patients). The low-grade type was noted in 50% of the mucoepidermoid cases. There were 2 cases (12.5%) of carcinoma ex pleomorphic adenoma.  There were 2 patients with non-Hodgkin malignant lymphomas who were diagnosed with the disease after immunohistochemistry diagnosis of the biopsy specimens. 
Malignant secondary tumors represented 18% of malignant pathology and 5% of all parotid tumors. The histological types were squamous cell carcinoma (2 cases) and malignant melanoma (1 case). The primary tumor was in the scalp region (parietal and frontal-temporal) for the squamous carcinoma and in the external ear for the melanoma. For the malignant cases, the WHO cancer staging was used: 38% were stage II (T2NOM0), 25% were stage I (T1NOM0) and III (T1/2N1M0), and 12% were stage IV (T4N0M0 or N2). 
30% of the malignant cases had facial nerve paralysis before surgery; more than 50% had abnormal vascular representation in the parotid region. All patients received surgical treatment followed by radiotherapy in 94% of the cases. In 37% of the malignant cases, parotidectomy was associated with modified radical neck dissection.
Regarding the surgical treatment, in 1.8% of the cases a simple tumor excision was performed (Whartin tumor). Partial parotidectomy was utilized in 70% of the benign cases (19 patients) with preservation of the facial nerve, except for one case that had the marginal branch in the tumor mass that had to be sacrificed. For the malignant pathology, total parotidectomy was the usual method of tumor resection; in 56% of the cases the facial trunk was preserved. 

Postoperatively, when the nerve was preserved, there was a temporary facial nerve paralysis in 22% of the cases, most likely due to intraoperative manipulation and the following edema, that resolved in 6 months for 83% of the patients. 
The Frey syndrome was noticed in 18% of the patients after 5-6 postoperative months, mainly in total parotidectomy cases, and in 3% of the cases after 3 years postoperatively. 
For mucoepidermoid carcinoma (low grade), the longest follow-up was 38 months postoperatively, with no signs of relapse. The 2-year survival for adenoid cystic carcinoma and high grade mucoepidermoid carcinoma was 70%. 

Discussion

The estimated incidence of parotid gland tumors is about 0.4-13.5 per 100,000 persons(4). The vast majority are benign tumors, pleomorphic adenoma being the most common, usually over 80%. The incidence in the present study was 70% for this pathology. Whartin tumor is ranked second place for benign parotid tumors; the authors found a percentage of 15% closely to other reports from the literature of 17%(5). 
The male to female ratio favored males, a possible explanation being that certain entities are highly found in males than females, such as the Whartin tumor; other authors report appropriate ratios, such as the Jordan study(6).
The youngest patient was 8-years-old, and the oldest was 78-years-old, with the median at 54-years-old. Usually, the peek incidence is in the 4th and 5th decade, similar to reports from other regions of the globe(7). Parotid masses are slow growing and don’t cause any pain for the patient. When the growth is accelerated pain starts to appear, or there are signs of epithelial vascular neoformation, or there are facial nerve dysfunctions, usually being a malignant process in the gland. 

The current study found that adenoid cystic carcinoma was the most encountered malignant pathology (31% of all cases and 9% of the malignancies), followed by mucoepidermoid carcinoma, similar to findings in the British population(8), although closer geographical reports put the mucoepidermoid carcinoma on the first place, such as the Greek study(9).
The facial nerve function was preserved in all benign cases except one case that had a branch crossing the tumor process and could not be detached from it. Regarding the malignant neoplasm, there was a 44% nerve sacrifice.
Malignant lymphoma of the parotid gland is a rare occurrence and has an incidence of 1-4%(10) of all parotid tumors, the present study finding an incidence of 3.5%.

Conclusions

The general findings of this study are similar to those found in other regions of the globe, although the incidence of malignant parotid pathology seems to be higher in recent years, and with particularity of non-Hodgkin lymphomas.