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Prospective Evaluation of Office-Based Parotid Ultrasound

From the Department of Surgery, Baylor University Medical Center, Dallas, Texas.

Correspondence: Address correspondence and reprint requests to: Joseph A. Kuhn, MD, Sammons Tower, Suite 420, 3409 Worth Street, Dallas, TX 75246-2096; Fax: 214-824-7167.

	ABSTRACT

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Background: Differentiation of parotid neoplasms from extraparotid upper cervical lesions is difficult by physical examination. The purpose of this report is to identify the role of office-based parotid ultrasound (US) in the evaluation of periauricular masses.

Methods: A prospective database including the results of physical examination, office-based US, and the corresponding pathology was reviewed. Soft-tissue US was performed with a 7.5-mHz parallel probe with biplanar imaging.

Results: Thirty-eight patients were evaluated over a 28-month period (mean age, 45 years; range, 23–78 years). US demonstrated a mass within the substance of the parotid (n = 23, 61%), outside the parotid (n = 11, 29%), or diffuse parotitis (n = 4, 10%). Intraparotid masses were preauricular (n = 14), postauricular (n = 5), or upper cervical (n = 4) and were solid (n = 22) or cystic (n = 1). Patients with solid intraparotid masses underwent superficial (n = 20) or total parotidectomy (n = 2). Benign (n = 19) and malignant (n = 3) solid parotid nodules had similar US features of hypoechogenicity with posterior enhancement. Indistinct margins were noted in 3 of 3 malignant lesions as well as 15 of 19 benign nodules (P = .9). Extraparotid masses were confirmed to be nodal disease on the basis of observation with resolution (n = 3), fine-needle aspiration (n = 6), or surgical removal (n = 2) (mean follow-up, 6 months).

Conclusions: Surgical office-based parotid US can delineate the location of periauricular mass lesions relative to the parotid gland. Benign and malignant lesions have a similar sonographic appearance.

Key Words: Parotid ultrasound • Parotid neoplasm • Upper cervical lesions • Office based

	INTRODUCTION

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The preoperative differentiation of intraparotid neoplasms from surrounding upper cervical lesions can be difficult by physical examination alone. Accurate localization is essential because the differential diagnosis and treatment of a parotid mass are quite different from those of extraparotid lesions. Traditional imaging for suspected parotid pathology includes sialography, computed tomography (CT), and magnetic resonance imaging. Even with these studies, it can be difficult to distinguish an intraparotid lesion from a regional lymph node or a subcutaneous nodule.

Surgeons have increasingly used ultrasound (US) to evaluate abdominal trauma, breast disease, and thyroid lesions and to localize abdominal pathology during surgery. US examination is painless, is noninvasive, requires no radiation exposure, and is easily performed. Although superficial periauricular lesions lend themselves to US, there are very few reports on the role of US in the diagnosis and treatment of salivary neoplasms. The purpose of this prospective study is to evaluate the clinical utility of office-based parotid US in the management of patients with periauricular lesions.

	MATERIALS AND METHODS

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A prospective database was compiled that was based on patients presenting to a single office with periauricular masses for a consecutive 28-month period. All patients underwent a detailed physical examination and were evaluated with sonography performed by two surgeons previously trained and experienced with soft-tissue sonography in the head and neck. Sonograms were performed with a 7.5-mHz parallel probe with biplanar imaging (Siemens Sonoline^TM, Germany). Lesions were defined as being intraparotid if they were circumferentially surrounded by parotid tissue. Data were collected regarding the individual appearance of each lesion, including echogenicity, presence of anechoic or cystic regions, borders, and shape of the mass. All patients with solid intraparotid lesions were offered surgical resection. Pathologic evaluation of resected surgical specimens was correlated with preoperative sonographic characteristics. Further routine imaging was not obtained in this group of patients, and fine-needle aspiration (FNA) was performed at the discretion of the examining surgeon. A further goal of the study was to determine the clinical accuracy and utility of sonography in the office setting.

Statistical analysis was performed with a z-test to assess statistical significance between sample proportions (StatView^TM, version 5.0, SAS Institute Inc., Cary, NC). Significance was defined as P < .05.

	RESULTS

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Thirty-eight patients were evaluated with a mean age of 45 years (range, 23–78 years). All presenting lesions were solitary and unilateral. The physical location of mass lesions and sonographic relation to the parotid gland are shown in Fig. 1. These data show that 30% of preauricular masses were actually not in the parotid gland. Intraparotid lesions were either solid (n = 22) or cystic (n = 1). FNA was performed with sonographic guidance on one cystic mass and six solid masses. The cystic lesion resolved, and cytology of solid lesions revealed pleomorphic adenoma (n = 3), Warthin’s tumor (n = 1), and poorly differentiated malignancy (n = 1) and was nondiagnostic in one case. All patients with solid intraparotid lesions based on sonography underwent surgical excision consisting of superficial parotidectomy (n = 20) or total parotidectomy (n = 2). Final pathology is shown in Fig. 2. Nonneoplastic benign lesions included chronic granulomatous disease (n = 2), chronic sialadenitis (n = 2), and pilomatrixoma (n = 1). In all 22 cases in which a solid intraparotid mass was found sonographically, its location was correctly predicted and confirmed pathologically.

View larger version (29K): [in this window] [in a new window]   FIG. 1. Physical and sonographic location of presenting masses.

View larger version (30K): [in this window] [in a new window]   FIG. 2. Pathology of surgically resected specimens.

Eleven patients with extraparotid masses were determined to have benign nodal disease on the basis of observation with resolution (n = 3), FNA (n = 6), or surgical excision (n = 2). At a median follow-up of 6 months (range, 2–18 months) no patient with sonographic extraparotid lesions has subsequently represented with a parotid mass. Four patients were found to have diffusely enlarged parotid glands, all of which resolved with observation.

Correlating sonographic findings with pathology revealed 3 of 3 malignant lesions to have ill-defined borders, whereas 15 of 19 benign lesions were described before surgery as having similar findings (P = .9). All solid lesions were described as hypoechoic with posterior acoustic enhancement. The cystic lesion was anechoic. The most common preoperative finding of pleomorphic adenoma was lobular shape (5 of 9), but 3 of 13 other intraparotid lesions were also described as lobular (P = .26). Both Warthin’s tumors were described as having multiple hypoechoic areas (2 of 2), and 3 of the other 20 solid lesions had similar findings (P = .06).

	DISCUSSION

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The correct preoperative localization of a periauricular lesion is essential to the surgeon. It can be very difficult for the surgeon to distinguish a periauricular node or subcutaneous mass from an intraparotid mass. US has been shown to be as sensitive as CT in accurately localizing superficial parotid lesions.^1–4 Corr et al.⁴ directly compared both imaging modalities in 40 patients and found the sensitivity of US and CT in detecting parotid lesions to be 100% and 97.5%, respectively. Corr and others generally recommend that CT be reserved for evaluating suspected deep-lobe or extensive parotid lesions.^2,4 This study also confirms the accuracy of office-based parotid US in correctly localizing 22 lesions into the parotid gland without the need for additional imaging studies. These were all confirmed by subsequent parotidectomy and pathologic analysis. Moreover, US correctly identified additional lesions that were not inside the parotid gland, thereby avoiding preparation for parotidectomy.

Many studies report a variety of sonographic features of different parotid lesions.^3,5,6 There are usually several descriptive factors for each specific lesion, making a diagnosis based on sonographic characteristics alone difficult. In a study of 86 parotid lesions, Shimizu et al.⁵ found lobular shape and homogeneous internal echoes predictive of pleomorphic adenoma and multiple anechoic areas predictive of Warthin’s tumor, with very high sensitivity. This study also found malignant tumors to be heterogeneous without a characteristic structure or shape. In a series of 289 parotid tumors, Gritzmann⁶ found 28% of malignant parotid tumors to have sharp margins. Others report up to 80% to 87% accuracy with using US to distinguish between benign and malignant parotid lesions.^7,8 This study failed to find diagnostic features of individual parotid lesions to predictably attain a diagnosis. Both benign and malignant lesions were hypoechoic with posterior acoustic enhancement. Although we often observed lobular shape in pleomorphic adenomas and multiple hypoechoic areas in Warthin’s tumors, theses characteristics were not statistically predictive of the histology. When FNA was performed with US guidance, the correct diagnosis was obtained in five of six patients before surgery. Five benign nonneoplastic lesions were surgically removed in this study, as would be expected given the inability of US to definitively characterize intraparotid solid lesions.

Surgeons have increasing experience with US. Studies have shown that surgeons can perform and interpret US examinations in a variety of settings, including acute abdominal trauma, critically ill intensive care patients, and breast, thyroid, vascular, endorectal, and intraoperative evaluations.^9,10 The American Board of Surgery recently included a "working knowledge of ultrasonography" in its definition of the scope of surgical practice.¹¹ As such, it is our view that office-based parotid US is a natural extension of the surgeon’s practice. This study further validates the utility of US in suspected parotid neoplasms because it accurately localizes these lesions. The surgeon is best served with preoperative information regarding the need for parotidectomy as opposed to simple excision of a periauricular lesion.

	Footnotes

 
Presented at the 54th Annual Meeting of the Society of Surgical Oncology, Washington, DC, from March 15–18 2001.

Received for publication March 16, 2001. Accepted for publication July 16, 2001.

	REFERENCES

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4. Corr P, Cheng P, Metreweli C. The role of ultrasound and computed tomography in the evaluation of parotid masses. Australas Radiol 1993; 37: 195–7.[Medline]
5. Shimizu M, Ussmuller J, Hartwein J, et al. Statistical study for sonographic differential diagnosis of tumorous lesions in the parotid gland. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1999; 88: 226–33.[CrossRef][Medline]
6. Gritzmann N. Sonography of the salivary glands. AJR Am J Roentgenol 1988; 153: 161–6.
7. Wittich GR, Scheible WF, Hajek PC. Ultrasonography of the salivary glands. Radiol Clin North Am 1985; 23: 29–37.[Medline]
8. Bruneton JN, Mourou MY. Ultrasound in salivary gland disease. ORL J Otorhinolaryngol Relat Spec 1993; 55: 284–9.[Medline]
9. Rozycki GS. Surgeon-performed ultrasound. Its use in clinical practice. Ann Surg 1998; 228: 16–28.[CrossRef][Medline]
10. Gogel BM, Ferry KM, Livingston SA, et al. The effect of surgical office-based thyroid ultrasound on clinical decision making. BUMC Proc 2000; 13: 207–9.
11. American College of Surgeons. Courses on ultrasound planned for general surgeons. Bull Am Coll Surg 1996; 81: 53.

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