A Clinicopathological Study of Parotid Gland Tumours
Authors: Ashitha P. , Thomas M. Jacob , Ponnappan Sheena , Kumar Sunil 
Published: August 2024

Abstract

Background:
The parotid gland is the largest salivary gland. Pleomorphic adenoma (PA) is the most common tumour found in the parotid gland. Most of the parotid tumours are painless and slow-growing. Ultrasound, computed tomography and magnetic resonance imaging are modalities of diagnosis. Fine-needle aspiration cytology (FNAC) is done in some cases, and its use is controversial.

Aim:
This clinicopathological study mainly aims at the demographic profile of the patient and clinical implications. Investigations were done and also evaluating the efficacy of FNAC in diagnosing parotid gland tumours.

Materials and Methods:
We conducted a prospective, hospital-based, observational study at our institution from December 2020 to June 2022. Forty patients who satisfied the inclusion and exclusion criteria were enrolled in the study. The study was analysed using SPSS version 25 developed by IBM. The categorical variables were presented as frequency and continuous data as mean, standard deviation (SD) and range with confidence interval. Categorical variables were compared using the Chi-square test; P <0.05 is considered significant. The sensitivity, specificity positive predictive value (PPV) and diagnostic accuracy of FNAC against the gold-standard histopathological examination (HPE) were worked out. The results are shown in tabular and graphical format.

Results:
The incidence of swelling was higher in males than females. Swelling was the most common clinical feature of the parotid gland. The duration of the disease ranges from ½to 48 months with an SD of 8.26 and a 95% confidence interval. One patient presented with facial nerve involvement and one patient presented with lymph node involvement. Five patients gave a history of surgery done in the past, which indicates recurrence, 10 (25%) patients were smokers and 1 (3%) patient had a history of previous radiation. Amongst the population of smokers, Warthin’s tumours were the most common (50%), PA (20%), oncocytic lipoadenoma, mucoepidermoid (MEP) carcinoma and myoepithelial (MyoEP) tumours having 10% incidence. The radiological findings were evaluated showing PA in 72.5% of cases, Warthin’s in 7.5%, neoplasm in 7.5% and non-specific cyst parotitis in 2.5% each. One patient image shows features of malignancy. FNAC says that 67.5% were PA, 20% were Warthin’s cyst and non-specific cyst, MEP and inflammation, but in one patient, FNAC was inconclusive. Most of the study population underwent superficial parotidectomy (32.5%); 30% of the study group underwent superficial conservative parotidectomy, but 27.5% of patients underwent total conservative parotidectomy. About 2.5% of the study group underwent extracapsular excision and enucleation. However, 2 (5%) patients were done with simple excision only. After surgery, out of 40, 38 patients had neuropraxia which recovered on follow-up. The most common tumour was PA (67.5%), and Warthin’s (22.5%) malignant tumours like MEP and MyoEP were 5% and 2.5%, respectively. Rare benign tumours like oncocytic lipoadenoma were the finding of HPE in FNAC that was inconclusive in this case. The incidence of malignant tumours was more common in males than in females, and it was more common in the age group of 21–40 years. MEP carcinoma was the most common malignant tumour. The efficacy of FNAC was identified in terms of sensitivity, specificity, negative predictive value (NPV), PPV and diagnostic accuracy. The sensitivity for benign tumours was 91.89% and that for malignant tumours was 33.33%. The specificity was 33.33% for benign tumours and 100% for malignant tumours respectively. The PPV was 94.44% for benign and 100% for malignant tumours. NPV was 25% and 94.87%, respectively. The diagnostic accuracy was 87.5% and 95%.

Conclusion:
Although FNAC has some pitfalls, the high sensitivity, specificity and accuracy in diagnosing malignant lesions as evident from this study indicate that FNAC is a reliable diagnostic method when correctly performed and interpreted by an experienced cytopathologist. Not all parotid lesions are lumps are malignant. Most of the masses are benign in nature. FNAC is a simple, safe, painless and cost-effective method for easy diagnosis.