Accessory parotid gland tumours: 24 years of clinical experience

Abstract

The accessory parotid gland (APG) is salivary tissue anterior to and anatomically separate from the parotid gland. APG is a common anatomical variation, but APG tumours are extremely rare. The authors report 6 patients with APG tumours emphasizing the diagnosis, clinical features, indications and rationales for different treatment approaches. Patients with primary tumours of the parotid gland or APG tumours who underwent surgical treatment were included. APG tumours comprised 1.23% of overall parotid tumours (6/488) and had a malignancy rate of 33.3% (2/6). There were three male and three female patients with a mean age of 39 years (range 14–70 years). 5 of 6 parotidectomies entailed superficial lobectomy, while one was a total parotidectomy with composite resection of masseter muscle. Concomitant selective lymphadenectomy was carried out in 3 of 6 patients. At 5 years disease-free survival was 83.3%. Mean follow-up was 161 months (range 14–253 months). Although nonsalivary diagnoses frequently occur in the buccal area, APG tumours should be considered in every differential diagnosis in patients presenting with a mid-cheek mass. From oncosurgical, cosmetic and functional standpoints, treatment by facelift parotidectomy or ‘S-incision’ with concomitant superficial lobectomy is the recommended surgical approach; high-grade malignancies require total parotidectomy with regional lymphadenectomy.

The evaluation of a mid-cheek mass represents a significant diagnostic and therapeutic challenge. Benign and malignant lesions in this area may arise from soft tissues of the face, including the skin, lymphatics, skin adnexa, neural, and salivary structures.

The accessory parotid gland (APG) has been described as salivary tissue that is anterior to and anatomically separate from the main body of the parotid gland and adjacent to Stensen’s duct by way of one or multiple secondary connections. Frommer, in his study of cadaveric dissections, found an APG in 21% of individuals, although some authors reported incidences as high as 56%. Although the APG is a common anatomical variation, APG tumours are extremely rare, with a reported incidence of 1–7.7% of all parotid gland tumours, and a malignancy rate from 26 to 50%. 157 lesions arising from APG have been reported in the English-language literature, including 54 malignant tumours, 80 benign tumours, and 23 nontumour lesions. There are few larger series describing APG tumours. To the authors’ knowledge, this is the second largest European series regarding APG tumours. The authors report 6 patients with APG tumours with emphasis on the diagnosis, clinical features, indications and rationale for different treatment approaches.

Materials and methods

Patients were identified through a database search of salivary gland tumours at the Department of Maxillofacial Surgery, University of Zagreb School of Medicine, University Hospital Dubrava, for the period between 1 January 1985 and 31 December 2008. Patients with primary tumours of the parotid gland or APG tumours who underwent surgical treatment were included. Among these tumours, patients with primary parotid gland tumours and patients with anterior process or extension of the main parotid gland were analysed separately from patients with primary APG tumours. Patients with normal salivary tissue in accessory parotid lobes and patients with heterotopic (ectopic) salivary gland tissues were excluded. The medical records of patients who were surgically treated for APG tumours were reviewed. Radiotherapy was indicated in cases of malignant disease of the APG. Follow-up intervals were calculated in months from the date of first treatment at the authors’ department to the date of last follow-up or death. The follow-up interval was concluded on 31 December 2011.

Results

During the 24-year period, 488 patients with primary parotid tumours underwent surgical treatment. APG tumours comprised 1.23% of overall parotid tumours (6/488) and had a malignancy rate of 33.3% (2/6). The clinical features, diagnosis, treatments and outcomes are summarized in Table 1 .

Table 1
Review of six cases of APG tumours.
Patient no. Age (y) Sex Presence of mass (mo) Symptoms Size (cm) Diagnosis Management Outcome
1. 14 M 3 Cheek swelling, pain mass 3.0 × 1.0 High-grade mucoepidermoid carcinoma Total parotidectomy, SND a (level 2) DOD b
2. 48 F 12 Firm, asymptomatic and progressively enlarging mass Multilocular Pleomorphic adenoma Superficial parotidectomy, SND (level 2) NED c
3. 70 M 216 Firm, asymptomatic and progressively enlarging mass 3.0 × 2.0 Pleomorphic adenoma Superficial parotidectomy NED
4. 67 M 36 Firm, progressively enlarging, pain mass 3.0 × 2.5 Adenoid cystic carcinoma Superficial parotidectomy, SND (level 1, 2) NED
5. 15 F 24 Firm, asymptomatic and progressively enlarging mass 1.2 × 1.0 Myoepithelioma Superficial parotidectomy NED
6. 20 F 24 Painless subcutaneous nodule, numbness of cheek and upper lip 1.7 × 1.7 Pleomorphic adenoma Superficial parotidectomy NED
Abbreviations

a Selective neck dissection.

b Died of disease.

c No evidence of disease.

There were three male and three female patients with a mean age of 39 years (range 14–70 years). All patients except one had undergone no previous treatment. The latter patient is a 48-year-old woman who received surgical treatment for a pleomorphic adenoma elsewhere (mid-cheek incision directly over the tumour) and was referred to the authors’ department because of local recurrence ( Fig. 1 ).

Fig. 1
Preoperative photograph showing scar (arrow) from mid-cheek incision.

Three patients presented with a painless, progressively enlarging buccal mass, while two patients had painful lesions at the same location. One patient had painless mid-cheek lesion with numbness of the cheek and upper lip.

All patients had undergone fine needle aspiration biopsy preoperatively and the results were identical to those provided by pathohistological analysis following operation. Histologically, of the 6 APG tumours, there were three pleomorphic adenomas (one of which was multilocular), one myoepithelioma, one adenoid cystic carcinoma and one high-grade mucoepidermoid carcinoma. Two patients with malignant disease underwent adjuvant postoperative irradiation which included 27 fractions of 2 Gy given over 4 weeks. 5 of 6 parotidectomies entailed a superficial lobectomy, while one was a total parotidectomy with composite resection of the masseter muscle in case of high-grade mucoepidermoid carcinoma. In four cases of superficial parotidectomy, buccal branches were in intimate relationship with the APG tumour and were sacrificed in order to achieve macroscopic tumour clearance. Apart from these patients in whom the facial nerve was partially sacrificed, two patients developed a facial palsy which fully recovered. Concomitant neck dissection was carried out in 3 of the 6 patients (50%), and comprised two selective neck dissections of level 2 and one selective neck dissection of levels 1 and 2. Lymphadenectomies were electively performed in suspicious cases, though they yielded negative neck nodes. No postoperative complications were detected.

At the time of follow-up, five patients were disease-free, while one patient developed a locoregional recurrence with distant metastases of a high-grade mucoepidermoid carcinoma 8 months after initial surgical intervention and died 6 months later. At 5 years disease-free survival was 83.3%. Mean follow-up was 161 months (range 14–253 months).

Results

During the 24-year period, 488 patients with primary parotid tumours underwent surgical treatment. APG tumours comprised 1.23% of overall parotid tumours (6/488) and had a malignancy rate of 33.3% (2/6). The clinical features, diagnosis, treatments and outcomes are summarized in Table 1 .

Table 1
Review of six cases of APG tumours.
Patient no. Age (y) Sex Presence of mass (mo) Symptoms Size (cm) Diagnosis Management Outcome
1. 14 M 3 Cheek swelling, pain mass 3.0 × 1.0 High-grade mucoepidermoid carcinoma Total parotidectomy, SND a (level 2) DOD b
2. 48 F 12 Firm, asymptomatic and progressively enlarging mass Multilocular Pleomorphic adenoma Superficial parotidectomy, SND (level 2) NED c
3. 70 M 216 Firm, asymptomatic and progressively enlarging mass 3.0 × 2.0 Pleomorphic adenoma Superficial parotidectomy NED
4. 67 M 36 Firm, progressively enlarging, pain mass 3.0 × 2.5 Adenoid cystic carcinoma Superficial parotidectomy, SND (level 1, 2) NED
5. 15 F 24 Firm, asymptomatic and progressively enlarging mass 1.2 × 1.0 Myoepithelioma Superficial parotidectomy NED
6. 20 F 24 Painless subcutaneous nodule, numbness of cheek and upper lip 1.7 × 1.7 Pleomorphic adenoma Superficial parotidectomy NED
Only gold members can continue reading. Log In or Register to continue

Jan 24, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Accessory parotid gland tumours: 24 years of clinical experience
Premium Wordpress Themes by UFO Themes