Diagnostic investigation of parotid neoplasms: a 16-year experience of freehand fine needle aspiration cytology and ultrasound-guided core needle biopsy

Abstract

This study aimed to examine the diagnostic yield of fine needle aspiration cytology (FNAC) and ultrasound-guided core needle biopsy (USCB) in the diagnosis of parotid neoplasia. A 16-year retrospective analysis was performed of patients entered into our pathology database with a final diagnosis of parotid neoplasia. FNAC and USCB data were compared to surgical excision where available. One hundred and twenty FNAC, 313 USCB, and 259 surgical specimens were analyzed from 397 patients. Fifty-six percent of FNAC and 4% of USCB were non-diagnostic. One hundred and thirty-two (33%) patients had a final diagnosis made by USCB and did not undergo surgery. Surgery was performed in 257 (65%) patients, 226 (88%) of whom had a preoperative biopsy. Most lesions were benign, but there were 62 parotid and 13 haematological malignancies diagnosed; false-negative results were obtained in three FNAC and two USCB samples. The sensitivity and specificity of FNAC were 70% and 89%, respectively, and for USCB were 93% and 100%, respectively. This study represents the largest series of patients with a parotid neoplasm undergoing USCB for diagnosis. USCB is highly accurate with a low non-diagnostic rate and should be considered an integral part of parotid assessment.

A swelling in the parotid region provides a diagnostic clinical challenge, as the spectrum of pathologies presenting as a parotid mass is wide and it is not possible to reliably differentiate between benign, malignant, and non-neoplastic lesions on clinical grounds alone.

An accurate preoperative diagnosis of a parotid lesion is essential as surgery may be avoided in certain benign neoplasms and in many non-neoplastic lesions. Where the patient is considered too elderly or unfit for surgery, biopsy diagnosis will allow prognostication and consideration of other treatment options, such as radiotherapy. Core biopsy alone can provide sufficient tissue for typing and grading of malignant parotid tumours, including lymphoma, thus avoiding diagnostic surgical excision biopsy. Where surgery is required, preoperative diagnosis is an important determinant for operative planning, notably with the increased use of extracapsular, parotid-sparing dissection and to allow appropriate informed patient consent (in particular pertaining to facial nerve integrity and also possible nodal dissection in malignancy).

Open surgical excision biopsy (SEB), as a method of obtaining a histological sample, has long fallen out of favour due to the risk of tumour seeding, facial nerve injury, facial scarring, and fistula formation. Consequently non-surgical approaches to tissue diagnosis, particularly fine needle aspiration cytology (FNAC), have been adopted widely. However, there are significant variations in the performance of FNAC within different practice settings. Broadly, FNAC is capable of a high specificity in optimized circumstances, but has lower sensitivity ; thus the false-negative plus high non-diagnostic rate of FNAC are increasingly considered clinically unacceptable.

Ultrasound-guided core biopsy (USCB) has been described relatively recently in the diagnosis of parotid tumours and is developing into an established technique. Controversy remains, however, regarding the optimal method for obtaining a tissue diagnosis. This study aimed to evaluate the utilization and performance of clinician-performed non-guided FNAC and USCB in the diagnosis of parotid neoplasia over a 16-year period in a district general hospital.

Materials and methods

Ethical exemption was granted for the study; approval was not required for this retrospective study at our centre. Patients were identified from the pathology database for a 16-year period (March 1997 to June 2013). Specimens were entered into the APEX pathology database (medical database software) using specific Systematized Nomenclature of Medicine (SNOMED) topography and morphology codes for salivary gland neoplasms. All patients with a pathological diagnosis of parotid neoplasia were included in the study. If a presurgical biopsy was performed, the results of the biopsy (FNAC and/or USCB) were compared with the surgical specimen as reference standard. If surgery was not performed, the results obtained from USCB or FNAC would constitute the final diagnosis.

Patients were retrieved using the specific coding parameters for salivary gland and neoplasia as search criteria; all parotid neoplasms were selected. Non-neoplastic parotid lesions and submandibular and minor salivary gland lesions were excluded. Once histology specimens were identified, the patients’ complete prior and subsequent histology profiles were interrogated, and correlation was also made with patient records, radiology reports, and images from PACS (picture archiving and communication system).

The following data items were collated from the histology reports: (1) site and date of the biopsy. (2) For each sample, the technique used to provide the histological diagnosis was documented (i.e. FNAC, USCB, or SEB). (3) Needle gauge for USCB and the number of passes/samples. (4) For each patient, all relevant samples were collated for comparison (i.e. FNAC vs. USCB vs. SEB where available).

FNAC was performed freehand, without ultrasound guidance, by clinicians in the maxillofacial or ENT outpatient clinic. A 21-gauge needle was used without the need for local anaesthetic. The number of passes for FNAC was not recorded. Neither a cytologist nor a technician was present in the clinic at the time of sampling.

All USCB were carried out in the hospital radiology department where patients underwent an initial diagnostic ultrasound and would then proceed to biopsy, if indicated. The majority of USCB ( n = 306) were performed using an 18-gauge (1.2-mm) needle; the remainder ( n = 7) were performed using a 20-gauge (1.0-mm) needle. USCB was performed using an automated biopsy device with a variable throw facility of 15–22 mm (Magnum Gun; Bard, Covington, GA, USA) using the technique described previously.

Standard calculations to determine the sensitivity, specificity, and accuracy of FNAC and USCB were then performed. For statistical analysis, the FNAC/USCB diagnosis was compared with the final surgical histology where available, with surgery considered the reference standard. Non-diagnostic results were excluded from these calculations.

Also evaluated were the results of FNAC and USCB in patients who had both procedures during investigation of the same lesion, actual findings following non-diagnostic FNAC and USCB where available, the number of cases with more than one FNAC or USCB during the work-up of the tumour, and the number of cases operated on with no firm preoperative diagnosis. We analyzed how often a diagnosis of malignancy was available preoperatively and the performance of USCB and FNAC in the diagnosis of haematological malignancy (i.e. how many cases were diagnosed and treated on the results of USCB or FNAC alone and how many required subsequent surgical excision for precise diagnosis).

Definitions

A non-diagnostic biopsy result was defined as a biopsy where definitive cytology/histology was not obtained. Also considered non-diagnostic were results where no firm diagnosis was reached, where the pathology report was equivocal (e.g. either reactive lymph node or low grade lymphoma) or likely not representative (inflammation only or necrotic material only).

A false-negative biopsy result was one where histology indicated benign disease but the final surgical diagnosis was confirmed as malignancy. A false-positive biopsy result was one where histology indicated malignant disease but the final diagnosis obtained at surgery was confirmed as benign disease. A true-negative biopsy result was one where histology indicated a benign neoplasm and this was confirmed on final surgical diagnosis. A true-positive biopsy result was one where histology indicated a malignant neoplasm and this was confirmed on final surgical diagnosis.

A therapeutic excision was one where a histological diagnosis, from biopsy, was available prior to surgery and subsequent surgery was performed for therapeutic purposes. A primary diagnostic surgical excision was a surgical excision without any previous biopsy being performed. In this circumstance, surgery was performed for diagnosis and for treatment. A secondary diagnostic surgical excision was a surgical excision performed when a prior sample from FNAC/USCB had been non-diagnostic.

Results

There were 200 female and 197 male patients with an age range of 21–104 years (mean age 67 years). A primary diagnostic surgical excision was performed in 31 patients (7.8%). Of the 397 patients, 305 had USCB and 110 had FNAC. Eight repeat USCB and 10 repeat FNAC were undertaken, giving a total of 313 USCB and 120 FNAC. Surgery was performed in a total of 257 patients (including the 31 primary excisions); two patients had further surgery for recurrence of malignancy. Among USCBs, 33.1% of patients (101/305) had one pass, 54.1% (165/305) had two passes, 11.1% (34/305) had three passes, and 1.6% (5/305) more than three passes.

The range of diagnoses obtained is shown in Table 1 . Note that of the 120 FNAC specimens, 53 (44.2%) were adequate, and of 313 USCB specimens, 300 (95.8%) were considered adequate to obtain a cytological diagnosis. Sixty-seven patients (55.8%) had an initial non-diagnostic FNAC, compared with 13 (4.2%) non-diagnostic USCB (see Table 2 ). Of these, eight FNAC and two USCB were repeated and 14 of the FNAC patients proceeded to USCB. Of the 67 patients with an initial non-diagnostic FNAC, malignancy was later confirmed in 29 (43.3%), compared with four (30.8%) of the 13 non-diagnostic USCB. The remainder of the non-diagnostic samples were confirmed as benign, except for two; one patient had a non-diagnostic FNAC for suspected recurrence of a squamous cell carcinoma and was not further investigated due to disseminated disease; another patient had a non-diagnostic USCB which was not further investigated. Table 3 shows the final diagnosis in patients who had a non-diagnostic biopsy and the method by which this was obtained.

Table 1
Range of diagnoses obtained from the diagnostic ultrasound-guided core needle biopsy (USCB), fine needle aspiration cytology (FNAC), and surgical excision biopsy (SEB) samples.
FNAC USCB SEB
Normal tissue 2 2
Benign
Pleomorphic adenoma 27 112 131
Warthin’s tumour 13 112 63
Oncocytoma 9 4
Basal cell adenoma 9 6
Mononuclear adenoma 2
Oxyphilic adenoma 5 2
Myoepithelioma 2
Microepithelioma 1
Mucous cyst adenoma 1
Lipoma 1
Malignant
Mucoepidermoid carcinoma 4 5 10
Adenocarcinoma 1 7 8
Squamous cell carcinoma 5 10 11
Acinar cell carcinoma 4 2
Adenoid cystic carcinoma 2 3
Basal cell adenocarcinoma 2
Large cell carcinoma 1 1
Undifferentiated carcinoma 1 1
Keratinizing SCC 1 1
Non small-cell carcinoma 1 1 1
Oncocytic carcinoma 1 1
Fibromyxoid sarcoma 1
Malignant melanoma 2 1
Myoepithelial carcinoma 2
Haematological
Non-Hodgkin lymphoma 3 1
MALT lymphoma 2 3
Plasmacytoma 2 1
Chronic lymphatic leukaemia 1
B-cell lymphoma 2 1
Follicular lymphoma 1
Total 53 300 259
SCC, squamous cell carcinoma; MALT, mucosa-associated lymphoid tissue.

Table 2
Spectrum of pathology findings in non-diagnostic fine needle aspiration cytology (FNAC) and ultrasound-guided core needle biopsy (USCB) results.
FNAC Insufficient material 37
Atypia – suspicious for malignancy but not diagnostic 13
No tumour cells seen but not definitive 10
Probable benign neoplasia but not diagnostic 3
Equivocal result between benign and malignant pathology 2
Haematoma 2
Total non-diagnostic FNAC 67
USCB Insufficient tissue 5
Atypia – suspicious for malignancy but not diagnostic 3
No tumour cells seen but not definitive 2
Equivocal result between benign and malignant pathology 3
Total non-diagnostic USCB 13

Table 3
Final diagnosis with initial non-diagnostic fine needle aspiration cytology (FNAC) and ultrasound-guided core needle biopsy (USCB).
Initially non-diagnostic FNAC
Surgical excision Warthin’s tumour 15
Pleomorphic adenoma 19
Myoepithelioma 1
Mucous cyst adenoma 1
Mucoepidermoid carcinoma 4
Adenocarcinoma 2
Basal cell adenocarcinoma 1
Squamous cell carcinoma 3
Fibromyxoid sarcoma 1
Lymphoma 1
Adenoid cystic carcinoma 3
Malignant melanoma 1
Subtotal 52
USCB Warthin’s tumour 10
MALT lymphoma 2
Adenocarcinoma 1
Pleomorphic adenoma 1
Subtotal 14
Total 66
Initially non-diagnostic USCB
Surgical excision Warthin’s tumour 4
Pleomorphic adenoma 3
Squamous cell carcinoma 1
Basal cell carcinoma 1
MALT lymphoma 2
Subtotal 11
USCB Pleomorphic adenoma 1
Subtotal 1
Total 12
MALT, mucosa-associated lymphoid tissue.

There were 140 patients who underwent USCB, FNAC, or both, but did proceed to definitive surgery. Two patients had non-diagnostic biopsies but were not investigated further. In 132 of the remaining 138 patients (95.6%), the final diagnosis was made by USCB alone. Of the other six patients, three were diagnosed by FNAC alone and three required USCB for non-diagnostic FNAC. Table 4 demonstrates the spectrum of diagnoses in the non-surgical group. The majority were benign (52.3% (72/138) Warthin’s tumour). Of the 11 patients with malignancy, seven were considered inoperable due to disseminated disease and four were unfit for surgery.

Table 4
Diagnoses obtained by ultrasound-guided core needle biopsy (USCB) and fine needle aspiration cytology (FNAC) in patients where no definitive surgery was performed.
USCB alone
Benign neoplasia Warthin’s tumour 68
Pleomorphic adenoma 31
Mononuclear adenoma 1
Lipoma 1
Myoepithelioma 2
Oncocytoma 8
Basal cell adenoma 3
Subtotal 114
Malignant neoplasia Adenocarcinoma 4
Squamous cell carcinoma 3
Acinar cell carcinoma 2
Mucoepidermoid carcinoma 1
Melanoma 1
Subtotal 11
Haematological malignancy Follicular lymphoma 1
Large B-cell lymphoma 2
MALT lymphoma 1
Chronic lymphocytic leukaemia 1
Non-Hodgkin lymphoma 1
Plasmacytoma 1
Subtotal 7
FNAC and USCB
Benign neoplasia Warthin’s tumour 2
Pleomorphic adenoma 1
Subtotal 3
FNAC alone
Benign neoplasia Warthin’s tumour 2
Pleomorphic adenoma 1
Subtotal 3
Total 138
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Jan 17, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Diagnostic investigation of parotid neoplasms: a 16-year experience of freehand fine needle aspiration cytology and ultrasound-guided core needle biopsy
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