A clinicopathological study of morphological pattern and management of parotid tumours : a multicentric experience

Result and discussion The mean age of presentation in our study was comparable with other series [9,10]. Pleomorphic adenoma was most common with 51 (41.5%) patients and Warthin's tumour was 2nd most common with 19 (15.4%) patients. Permanent facial nerve palsy was seen in 0.04% of our patients. Pain (41.3%) and swelling (100%) were the most frequent presenting feature of malignancy. 15 (34%) patients with malignant tumour required additional reconstruction by pectoralis major myocutaneous flap.


Introduction
Salivary gland tumours are heterogeneous neoplasms with complex morphology and dubious clinical characters. They represent about 3% of all tumours and 5-6% of all head and neck tumours. 80% of these tumours are located in the parotid gland, of which, 80% are benign, limited in lower part of the gland and 80% of them are pleomorphic adenomas. Ninety percent of them arise from the superficial lobe [1]. These tumours represent a challenging clinical entity to the clinicians due to their wide spectrum of presentation, inconsistent clinical features, management protocols and unpredictable prognosis.
Parotid tumours are more frequent in females. Ionising radiation, exposure to sunlight, chemotherapy, smoking, Vitamin A deficiency, geographic location and ethnicity have been linked with their incidence. They appear as slow growing tumours with a visible swelling in the parotid region being the only feature in majority of the cases. Rapid enlargement, tenderness or neuropathy often signifies malignancy, tuberculosis or sarcoidosis [2]. Common malignant tumours are adenoid cystic carcinoma, mucoepidermoid carcinoma and adeno-carcinomas.
Fine Needle Aspiration Cytology (FNAC) is often the first pathological investigation with sensitivity and specificity of approximately 95% and 75% [3]. Although CT scan helps in delineating the extent of the lump, involvement of deep lobe, parapharyngeal extension and relation to facial nerve, MRI is considered as investigation of choice [4]. Relationship of the tumour with facial nerve warrants careful and cautious dissection during parotid surgery because unintentional injury or sacrifice of facial nerve leads to lifelong disfigurement with discouraging result even after reanimation surgery .
The aim of our study was to assess the demographics, frequency, morphology, management and long term follow up results of the patients undergoing parotidectomy at three tertiary care centres of Kolkata between January 2011 to December 2015. Ninety eight (58.7%) out of 167 patients underwent superficial parotidectomy and 69 (41.3%) patients underwent total parotidectomy. Among 69 patients undergone total parotidectomy 25 were benign and 44 were malignant tumours. 25 patients with benign parotid tumours underwent total parotidectomy with facial nerve sparing as the tumour involved the deep lobe in addition to superficial lobe. 38 patients with malignant tumours had total parotidectomy with sparing of facial nerve macroscopically whereas 6 patients with malignant parotid tumours had total parotidectomy with facial nerve resection. Twenty nine patients underwent modified radical neck dissection with total parotidectomy because of palpable or radiologically significant neck nodes. Reconstruction by PMMC (Pectoralis Major Myocutaneous Flap) was required in 15 patients.

Materials and methods
Eight patients developed post-operative hematoma which settled with aspiration or evacuation. Eleven patients developed wound infection following operation which resolved with intravenous broad-spectrum antibiotics and regular dressing. Hundred and thirty four (80.24%) patients had transient facial nerve palsy (House Brackman Grade 2 or 3) that resolved with steroids or spontaneously with time within 2-8 weeks. 6 (0.04%) patients with severe facial nerve had complete facial nerve palsy (House Brackman Grade 6) [5]. The mean follow up period after surgery was 9 months with range of 1-18 months.
In the follow up period we found that all the benign cases remained healthy without any mortality, among the malignant cases 22 patients (13.2%) with high grade malignancies died because of local or distant recurrence, 12 patients (7.2%) with intermediate grade malignancies are living with the disease, in the form of either local or distant recurrence, rest 10 patients (6%) are living without any recurrence or residual disease . Inclusion criteria -all patients presenting with parotid tumours regardless of age and sex.

Results
Between January 2011 and December 2015, 167 patients underwent parotidectomy. Amongst them, 82 were male (49.1%) and 85 were female (50.9%). The mean age of presentation was 36 years for benign tumours with range between 22 -76 years and 48 years for malignant tumours with range between 25 -71 years. All the patients had FNAC performed prior to surgery. All the patients had CT / MRI scan performed before operation to assess the extent of the lesion.

Discussion
Salivary gland tumours are the most complex and morphologically diverse group of human tumours with different clinical features, varied morphology, dubious nature and unpredictable prognosis [6]. These tumours have infectious, granulomatous , auto-immune, obstructive, developmental, idiopathic and neoplastic etiology [7]. Most often they present as non-tender gradually progressive masses in respective regions. Most of them occur in the parotid gland and most of them are benign. Commonest form of benign salivary gland tumours is pleomorphic adenoma , both in major and minor salivary glands.
Incidence of parotid tumour is approximately 2.4/100,000/ year [8]. The mean age of presentation in our study was comparable with other series [9,10]. In contrast to literature, left sided tumours were more frequent and female preponderance was more in our study [11].
Benign tumours accounted for 73.6% of parotid tumour in this study. Pleomorphic adenoma was most common with 51 (41.5%) patients and Warthin's tumour was 2nd most common with 19 (15.4%) patients. Incidence of malignant tumours (26.3%) was compatible with other published data [12,13]. Mucoepidermoid carcinoma was the commonest malignant tumour of the parotid gland in the present study, 12 patients (27.3%) similar to literature.
All the patients had CT/MRI scan performed preoperatively to assess the extent of tumour and treatment planning. MRI was very useful particularly in patients with deep lobe involvement, suspected malignant tumours with local infiltration, recurrent cases and tumours extending to inaccessible areas such as retromandibular fossa or parapharyngeal space [14].
The incidence of transient facial nerve palsy was 68.26% in our study, higher than studies reported by Laccorreye [15] & Mehle [16]. Permanent facial nerve palsy was seen in 0.04% of our patients. Of the 6 cases who had complete nerve palsy, 3 had mucoepidermoid carcinoma, 2 had adenoid cystic carcinoma and 1 had poorly differentiated carcinoma with nerve entrapment. This result was similar to other studies (0-10%) [17].
Thorough anatomical knowledge and nerve stimulator are extremely necessary for facial nerve preservation. Patients with malignancy were preferentially treated with total parotidectomy with or without facial nerve sparing as compared to benign disease with a low threshold for nerve sacrifice.
Recurrence rate of pleomorphic adenoma in the present study was 8.1%, and rate of malignant transformation was 11.4% higher than many larger series (<2%) [18]. Surgery for these two entities was technically very challenging with increased morbidity and worse prognosis.
Pain (41.3%) and swelling (100%) were the most frequent presenting feature of malignancy in our study similar to the literature, however, skin or underlying tissue fixity and cervical lymphadenopathy have also been reported in other series as common features [19].

Conclusion
The current study is a prospective study of parotid tumours in three tertiary care hospitals of Kolkata over a span of 5 years. The approach was to study morphological and histopathological distribution of parotid tumours, classification, difficulties encountered during management and to compare with the observations in similar studies with special emphasis on incidence, age, sex and complication rates.
Our study found many similarities in clinical course of parotid tumours when compared to other parts of the world, as well as a few unique findings. Female preponderance was found with more tendency of left sided tumours. Average age of incidence was higher for malignant neoplasms than their benign counterparts . Pleomorphic adenoma was the most common benign parotid gland tumour and mucoepidermoid carcinoma was the most frequent malignant neoplasm . Surgery with optimum preoperative planning and counselling remains the mainstay of treatment . Prior and in-depth knowledge of regional anatomy with meticulous and careful planning and use of advance technology is essential to reduce the incidence of complications.