The accuracy of fine-needle aspiration cytology for diagnosis of parotid gland masses: a clinicopathological study of 114 patients

ABSTRACT Objective Fine-needle aspiration cytology is a valuable method for preoperative assessment of head and neck tumors. However, its accuracy in detection of salivary gland masses is controversial compared with other methods. The aim of this work was to evaluate the effectiveness and accuracy of fine-needle aspiration cytology (FNAC) in the diagnosis of parotid gland masses. Material and Methods Over a 10-year period, 126 parotid gland masses were resected. Retrospective chart reviews of 114 patients were performed. The results of FNAC and final histological diagnosis were compared and the accuracy of FNAC was determined. Results Final histological evaluation revealed 11 malignant tumors and 103 benign lesions. Pleomorphic adenoma was the most common neoplasm (63%), followed by Warthin’s tumor (17.5%). The sensitivity of FNAC in detecting malignant tumors was 73% and the specificity was 97%. Positive predictive value (PPV) was 73% and negative predictive value (NPV) was 97%. The overall accuracy of FNAC in detecting parotid masses was 95%. False-negative diagnosis was found in mucoepidermoid carcinoma, acinic cell carcinoma, and epithelial-myoepithelial carcinoma whereas there was false-positive diagnosis in cases of pleomorphic adenoma and normal parotid gland tissue. Conclusion FNAC is a reliable minimally invasive diagnostic method with a high sensitivity in diagnosis of lesions in parotid glands. The sensitivity of detection of malignant tumors in parotid glands was low due to the biopsy technique used, and depended on tumor location. Postoperative complications decreased after superficial parotidectomy.


INTRODUCTION
Salivary gland tumors are a morphologically and clinically diverse group of neoplasms, which may challenges. In the western world, the estimated overall incidence is approximately 2.5 3.0 cases per 100,000 per year 21 . Malignant salivary gland neoplasms account for more than 0.5% of all malignancies and approximately 3 5% of all head and neck cancers 21 . In Sweden, the incidence of parotid gland tumors is 0.77 cases per 100,000 women and 1.16 cases per 100,000 men. In comparison, the overall incidence of salivary gland tumors during the same year was 0.99 in women and 1.49 in men 7 . Several imaging modalities have been used for diagnosis of parotid masses, including magnetic resonance imaging (MRI) and computed tomography (CT) 16,28 . MRI provides anatomical information about parotid tumor location and can be a useful tool to determine whether the mass is benign or malignant 16 . Fine-needle aspiration cytology (FNAC) is a globally accepted method in the preoperative evaluation of head and neck tumors. This method provides excellent distinction between benign and malignant parotid tumors, and has other advantages: it is inexpensive, easy to perform, relatively painless, and well tolerated 1 . The procedure is a cytodiagnostic method whereby a needle is used to acquire a sample of cells and microparticles of tissue for morphological analysis. Compared with histological results, a concordance of a sensitivity of 84%, and a diagnostic accuracy of 94% 1 . However, the value of FNAC for the diagnosis of parotid gland masses. has been questioned due to its low sensitivity regarding malignancy, variation in reported results, and the belief that most parotid masses require surgery in any case 17,20 . Tumors of the parotid gland can be removed by 10 .
Enucleation of parotid gland masses is not the risk of recurrence 29 . Several complications have been associated with parotid gland surgery, such as facial nerve disturbance, Frey's syndrome, and great auricular nerve paresthesia 9,27 . Factors that affect facial nerve dysfunction include malignant tumors, lesion sizes, operating time, and type of 2,3,9,27 . The aim of this study was to evaluate the diagnostic value of FNAC in detection of parotid gland tumors at our clinic (especially for detection of malign lesions). a retrospective study. In addition, clinical outcome of surgery and postoperative parameters were also evaluated.

Ide o o s dy o o
Eskilstuna Hospital provides healthcare to more than a quarter of a million inhabitants. Over a 10year period (January 2003 to December 2014), masses in the salivary gland tumors of 126 patients were resected. Patients treated between January and December 2006 were excluded due to an error in the patients' electronic medical records. The medical records of 12 patients could not be located, so 114 patients (61 males and 53 females) with a mean age of 56.4 years (range 18-85 years) were included in this study for further investigation. Three surgeons performed the surgical procedures. Intraoperative facial nerve monitoring with a nerve stimulator was used in all cases. We used our department' to identify all patients who were diagnosed with a mass in the parotid gland. The ICD-10 codes D11.0, D11.9, C08.8, C08.9, and C07.9 were used to identify subjects from the database; this was the diagnosis.
Information regarding patient demographics, FNAC results, and final histological diagnosis results was evaluated. The postoperative outcome, including postoperative infection and hematoma, facial nerve disturbance, and Frey's syndrome was also registered. The preoperative FNAC results from the surgical specimens. Data on age, gender, tumor type, and postoperative complications (facial nerve disturbance, postoperative infection, Frey's syndrome, and hematoma) were collected from the clinical records. Facial nerve disturbance was classified into four categories: (1) none, (2) transient (0 2 months), (3) less transient (2 12 months), and (4) permanent. Patients with radiologically verified and FNAC-verified cysts in parotid glands were excluded. Patients with inconclusive FNAC results were also excluded.

Fine-needle aspiration cytology technique
FNAC was performed using a 22-gauge needle attached to a 10-mL plastic syringe mounted on a syringe holder for a single hand grip. The aspirated without using local anesthesia. The number of aspirations varied between 2 and 3, depending on the accessibility of the tumor. FNAC air-dried smears were stained with Giemsa stain and the slides were then examined under a light microscope (Olympus Cx31, Nishi Shinjuku 2-chome, Tokyo, Japan), and results were reported according to the World Health Organization guidelines regarding parotid gland neoplasm.
All FNAC samples and tumor specimens w e r e a n a l y z e d b y t h e s a m e l a b o ra t o r y (Unilabs Laboratoriemedicin at Mälarsjukhuset, diagnostikcentrum Eskilstuna, Sweden). Patients to the head and neck cancer center at Örebro University Hospital for further cancer treatment.

Statistics
FNAC-based diagnoses were compared with diagnoses from histological examination of specimens. We calculated the sensitivity regarding the presence of malignancy (true positive/true absence of malignancy (true negative/true negative + false positive), positive predictive value (PPV) (true positive/true positive + false positive), negative predictive value (NPV) (true negative/ true negative + false negative), and accuracy of FNAC (true positive + true negative/total). level. results are presented in terms of frequencies and percentages. Kappa value was also used to compare 2016;24(6):561-7 the agreement between the FNAC-based diagnosis and the biopsy-based diagnosis. Statistical analysis was carried out using SPSS (version 12.0).

Demographic and histological outcome
One hundred fourteen patients with parotid masses (61 males and 53 females) with a mean age of 56.4 years (range 18 85 years) were included in the study. Mean duration of follow-up was 66 months (range 3 132 months). The female-to-male ratio was approximately 1 to 1.1. Tumors were cases, 76%), but 27 tumors (24%) were in the deep parotid lobe. FNAC of the deep portion of parotid mass was conducted in 7 cases (6%), whereas in 20 cases (17.5%) this procedure was performed using ultrasound-guided biopsy.  Table 2). The kappa statistic for the degree of agreement between FNAC and histological results was 0.94.
In summary, the study showed low sensitivity for malignant tumors. However, regarding the location of tumors, these three false-negative cases were located in the deep portion of the parotid gland and they were diagnosed by FNAC without ultrasoundguided biopsy.

DISCUSSION
FNAC is a simple, inexpensive, and atraumatic method for preoperative assessment of tumors, lymph nodes, and other lesions in the head and neck. It is a safe procedure requiring minimal equipment, with a very low risk of cancer cell implantation 11,25 . Fine-needle aspiration of parotid glands may lead 5 .
Infarction or metaplastic transformation of benign tumor has also been mentioned in the literature 8 . In this study, there were a few cases of infection (5.8%), hemorrhage (0.8%), and Frey's syndrome (2.5%) as a result of FNAC of the parotid mass lesions. No long-term facial nerve dysfunction was observed 1 year after surgery.
Several imaging modalities have been used for diagnostics of parotid masses, including CTscan, MRI, and ultrasound-guided core needle biopsy (USCB) 15,16,28 . CT-scan and MRI provide information about size and location of the tumor. However, comparing these two methods, CT-scan accurately assesses parotid lesions while MRI shows the relationship to adjacent structures better 16,28 . In a clinical study by Inohara, et al. 16 (1993), the relative value of FNAC and MRI in relation to the differential diagnosis of benign and malignant parotid mass lesions was investigated. Eighty-one   13 (2015) reported the largest series of patients with parotid neoplasm who underwent USCB. One hundred twenty specimens were analyzed with FNAC, 313 were analyzed with USCB, and 259 surgical specimens were analyzed of FNAC were 70% and 89%, respectively, and by others 15 .

Reliability of FNAC
The importance of FNAC in distinguishing malignant parotid mass lesions from benign ones has been investigated by several authors 1,19 . Despite the simplicity of the method, the accuracy of FNAC varies depending on the precision and experience of pathologists 2 with FNAC are most common in lesions involving pleomorphic adenoma, basal cell adenoma, lowgrade mucoepidermoid carcinoma, and acinic cell carcinoma 3 in low-grade mucoepidermoid carcinomas where thick mucinous liquid is seen in the background with a paucicellular smear 3 . In such cases, malignant tumors are mistakenly reported as benign lesions 3 . This occurred with one of our patients with a tumor in the deep portion of the parotid gland ( Figure  1). The malignant tumor was assessed to be a benign tumor. Pleomorphic adenoma was one of the most common benign tumors in this study. Figure 2 shows cytological images of pleomorphic adenoma with its characteristic biphasic pattern, comprising epithelial/myoepithelial cells and In this study, of 103 cases of benign tumor, 100 cases were diagnosed using FNAC; of 11 malignant cases, 8 were diagnosed with FNAC. The overall accuracy of FNAC for parotid masses was estimated to be 95%, which is in the same range as in previous studies 4,12,[22][23][24]30 . False-negative  diagnosis was found in mucoepidermoid carcinoma (n=1; 1.4%), acinic cell carcinoma (n=1; 1.4%), and epithelial-myoepithelial carcinoma (n=1; 1.4%), and there was false-positive diagnosis in cases of pleomorphic adenoma (n=2; 2.7%) and in normal parotid tissue (n=1; 1.4%). Diagnosis of due to its extreme morphological heterogeneity; it may be misdiagnosed as Warthin's tumor or mucous retention cysts.

CONCLUSION
malignant parotid gland tumors, and provides the surgeon with valuable information in preoperative diagnostics. In this study, the sensitivity of FNAC in detection of malignant tumors was low due to the biopsy technique used, which depended on the location of the tumor. However, in cases where ultrasound guidance was used, 100% accuracy was achieved.