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Multiple primary pleomorphic adenomas in a single parotid gland: report of a new case. (Original Article).

Abstract

The development of multiple primary pleomorphic adenomas in a single parotid gland is extremely rare in previously untreated patients, as only nine cases have been previously reported. In this article, we report the tenth such case, which occurred in an 87-year-old Japanese woman. We also report the results of our 7-plus-year review of the types of parotid tumors seen at our institution. We identified 98 tumors in 89 patients; pleomorphic adenomas were the most common tumors, accounting for 45.9% of the total.

Introduction

The development of multiple separate tumors arising in a single salivary gland is rare in previously untreated patients. Most such masses are multifocal Warthin's tumors (adenolymphomas). The most common tumors of the salivary glands are pleomorphic adenomas (mixed tumors). Likewise, the incidence of multiple primary unilateral pleomorphic adenomas in previously untreated patients is extremely rare, as only nine cases have been previously reported. In this article, we report the tenth such case, and we review the literature on this condition.

Case report

An 87-year-old Japanese woman came to us for an evaluation of a left facial mass. Approximately 1 month earlier, she had noticed the lesion by chance. She denied pain, tenderness, discomfort, fever, facial nerve dysfunction, sensory disturbance, and xerostomia. She had no history of surgery, aspiration biopsy, or radiotherapy to the head or neck.

Our physical examination revealed the presence of a preauricular mass that was 24 x 22 mm in diameter and rather firm, smooth, and movable. Another mass was slightly palpable between the mastoid tip and the angle of the mandible. The patient's facial nerve function was completely normal.

Axial-plane computed tomography (CT) detected two round, discrete lesions in the left parotid gland. Intravenous contrast CT demonstrated a slight enhancement of the margin of the superior, superficial mass and a rather homogenous enhancement of the inferior, deep mass.

T1-weighted magnetic resonance imaging (MRI) showed a relatively homogenous, low signal intensity in both masses, while T2-weighted MRI showed a very high signal intensity in the superficial mass and an isosignal intensity in the deep mass (figure 1). A technetium 99m pertechnetate salivary scan revealed a cold spot in the left parotid, while 67Ga scintigraphy showed a hot spot there. Ultrasound examination of the parotid showed that the superficial lesion was oval and the deep lesion had some lobes. A tentative preoperative diagnosis of either multiple pleomorphic adenomas or a pleomorphic adenoma associated with a malignant lymphoma was made.

The patient underwent a left lateral superficial parotid lobectomy with facial nerve preservation. Intraoperative examination identified a smooth mass in the superior portion of the parotid gland anterior to the ear and another smooth mass between the mastoid tip and the angle of the mandible. The two masses were widely separate and discrete.

On gross pathology, the superficial and the deep nodules measured 17 x 13 mm and 18 x 10 mm, respectively. Both were clearly well encapsulated and surrounded by normal salivary gland tissue. The cut section of the superior tumor was softer than that of the inferior mass, and it contained a small amount of brown fluid (figure 2). The inferior tumor had a white, lobulated, and firm surface.

Microscopic analysis revealed that both tumors had a complete fibrous capsule and were separate from each other. The central space of the superior tumor contained prominent myxoid components. Several random small ducts and myoepithelial cells were darkly stained and spindle shaped (figure 3). The space near the capsule was made up primarily of ductal structures and myoepithelial cells. Similarly, the inferior tumor was made up primarily of ductal structures, and darkly stained, spindle-shaped myoepithelial cells surrounded the duct-lining cells (figure 4). Epithelial and myoepithelial cells formed the major part of the inferior tumor, and stromal components were difficult to find. No mitotic figures were observed.

The patient's postoperative course was uneventful, and her facial nerve functioned well. She was discharged on the eighth postoperative day. At follow-up i month later, the wound was well healed. Two years later, she has had no recurrence of either tumor.

Discussion

Several large studies have found that the pleomorphic adenoma, the most common tumor of the parotid gland, accounts for 55 to 65% of all parotid tumors. (1,2) It is also the most common tumor of all the salivary glands.

During the 7-plus years from June 1992 to November 1999, 89 patients with 98 parotid gland tumors were treated at our institution, the Himeji National Hospital in Japan (table 1). Of the 98 tumors, 91 were benign (92.9%), including 45 pleomorphic adenomas (45.9%). By contrast, Bardwil (3) found that pleomorphic adenomas accounted for only 24.0% of all parotid gland tumors, while Eneroth (4) reported a much higher figure of 70.9%.

Nine of the 89 patients at our institution had two distinct parotid tumors each (table 2). The development of multiple separate tumors in the salivary glands is rare in previously untreated patients. In many cases, these multiple masses were identified as Warthin's tumors. According to currently accepted theory, Warthin's tumors originate in salivary duct epithelium and acini that are enclosed by lymph nodes inside and outside the parotid gland. (5) Multiple Warthin's tumors are believed to arise when multiple lymphoid tissues become involved with these ductal epithelial elements.

In a study of 278 cases of Warthin's tumor, Eveson and Cawson found that 13 (4.7%) were bilateral. (6) Foote and Frazell found bilateral tumors in six of 44 patients (13.6%). (7) Warthin's tumor is also the most likely lesion to manifest multifocal unilateral involvement. Gnepp et al reviewed the records of 25 patients who had synchronous unilateral salivary gland tumors. (8) They found coexisting benign and malignant tumors in six patients (24.0%) and coexisting benign tumors (e.g., Warthin's tumors, pleomorphic adenomas, and oncocytomas) in 17 patients (68.0%). In our review of 89 patients with 98 parotid masses, we found that nine patients had synchronous tumors. Seven of these patients had Warthin's tumors--six unilaterally and one bilaterally.

Multiple pleomorphic adenomas of the major salivary glands are believed to arise under three circumstances: (1) as a recurrence after an incomplete excision of a tumor, (2) as a result of implantation during aspiration biopsy, and (3) as separate primary tumors:

Recurrence. Most cases of multiple pleomorphic adenomas are considered to be recurrences. (7) The multiple lesions arise as a result of the dissemination of residual fragments of tissue during surgery on the primary tumor. (9) Pleomorphic adenomas are well circumscribed and typically characterized by a smooth, fibrous, pseudocapsule that varies in thickness and completeness. This variance in structure is the reason the capsule is often penetrated by tumor tissue and destroyed.

The high rate of recurrence of pleomorphic adenomas has been attributed to their infiltrative and destructive growth. (10) Batsakis suggested that recurrence is also a consequence of rupture, seeding, or inadequate removal. (5) The two most likely reasons for recurrence are the poor structural character of a lesion and an incomplete excision. However, a change in surgical strategy from local excision to superficial or total parotidectomy has resulted in a decrease in the recurrence rate from 8 to 2%. (11) Recurrence can also be prevented by meticulous intraoperative inspection and palpation of the glandular tissue. At our facility, there were no recurrences among the 45 patients with pleomorphic adenomas who were available for follow-up, which ranged from 2 to 10 years.

Implantation. Tumor implantation during an aspiration biopsy is an important issue. (5) Eneroth described three cases of multiple unilateral pleomorphic adenomas of the parotid gland at sites where there had been a previous needle aspiration of the parotid. (4)

Primary tumor. The occurrence of multiple pleomorphic adenomas as primary tumors is extremely rare. Only nine cases have been previously reported. In 1953, Foote and Frazell described two cases; one patient had two pleomorphic adenomas in the same parotid gland, and the other had two pleomorphic adenomas in the right parotid and one in the left. (7) In 1954, Andre described a patient who had two pleomorphic adenomas in the right parotid. (12) Turnbull and Frazell described three cases in 1969. (13) In 1982, Behnke reported the case of a patient who had two pleomorphic adenomas in the right parotid. (14) Batsakis (15) described one case in 1986, and Franzen and Koegel (16) documented the ninth case of synchronous double tumors 10 years later.

We report the tenth such case, which was marked by the coexistence of two pleomorphic adenomas in the superficial lobe of the left parotid. We believe that the coexistence of the two tumors was the product of mere coincidence rather than the result of an association between the two.
Table 1

Types of parotid tumors (n = 98) in 89 patients seen at Himeji National
Hospital between June 1992 and November 1999

Type of tumor n (%)

Benign tumors 91 (92.9)
 Pleomorphic adenomas 45 (45.9)
 Warthin's tumors 27 (27.6)
 Lymphoepithelial lesions 10 (10.2)
 Other 9 (9.2)

Malignant tumors 7 (7.1)
 Adenoid cystic carcinomas 2 (2.0)
 Mucoepidermoid carcinomas 2 (2.0)
 Unclassified carcinomas 2 (2.0)
 Squamous cell carcinoma 1 (1.0)
Table 2

Types of synchronous parotid tumors found in nine patients

Type of tumor n

Unilateral Warthin's tumor 6
Bilateral Warthin's tumor 1
Unilateral pleomorphic adenoma 1
Unilateral lymphoepithelial lesion 1


References

(1.) Frazell EL. Clinical aspects of tumors of the major salivary glands. Cancer 1954;7:637-59.

(2.) Skolnik EM, Friedman M, Becker S, et al. Tumors of the major salivary glands. Laryngoscope 1977;87:843-61.

(3.) Bardwil JM. Tumors of the parotid gland. Am J Surg 1967;114:498-502.

(4.) Eneroth CM. Histological and clinical aspects of parotid tumours. Acta Otolaryngol Suppl 1964;191:12-4.

(5.) Batsakis JG. Tumors of the Head and Neck: Clinical and Pathological Considerations. 2nd ed. Baltimore: Williams and Wilkins, 1979.

(6.) Eveson JW, Cawson RA. Warthin's tumor (cystadenolymphoma) of salivary glands. A clinicopathologic investigation of 278 cases. Oral Surg Oral Med Oral Pathol 1986;61:256-62.

(7.) Foote FW, Frazell EL. Tumors of the major salivary glands. Cancer 1953;6:1065-133.

(8.) Gnepp DR, Schroeder W, Heffner D. Synchronous tumors arising in a single major salivary gland. Cancer 1989;63:1219-24.

(9.) Gaynor EB, Hershberg R. Unilateral multiple tumours of the parotid gland. J Laryngol Otol 1976;90:295-8.

(10.) Eneroth CM. Mixed tumors of major salivary glands: Prognostic role of capsular structure. Ann Otol Rhinol Laryngol 1965;74:944-53.

(11.) Woods JE, Chong GC, Beahrs OH. Experience with 1,360 primary parotid tumors. Am J Surg 1975;130:460-2.

(12.) Andre MP. Double tumeur mixte de la parotide. Ann Otolaryngol 1954;71:474-5.

(13.) Turnbull AD, Frazell EL. Multiple tumors of the major salivary glands. Am J Surg 1969;118:787-9.

(14.) Behnke EE, Jr. Unilateral multiple benign mixed tumors of the parotid gland. Laryngoscope 1982;92:1265-8.

(15.) Batsakis JG. Recurrent mixed tumor. Ann Otol Rhinol Laryngol 1986;95:543-4.

(16.) Franzen A, Koegel K. [Synchronous double tumors of the parotid gland]. Laryngorhinootologie 1996;75:437-40.

From the Department of Otolaryngology, Himeji National Hospital, Hyogo, Japan.

Reprint requests: Hitoshi Tanimoto, Department of Otolaryngology, Kobe University School of Medicine, 7-5-2 Kusunoki-chou, Chuou-ku, Kobe 650-0017, Japan. Phone: +81-78-382-6024; fax: +81-78-382-6039; e-mail: hitoshi@tc4.so-net.ne.jp

This work was financially supported by a grant-in-aid for cancer research (9-16) from the Ministry of Health and Welfare, Japan.
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Comment:Multiple primary pleomorphic adenomas in a single parotid gland: report of a new case. (Original Article).(Statistical Data Included)
Author:Hirayama, Yuji
Publication:Ear, Nose and Throat Journal
Article Type:Statistical Data Included
Geographic Code:9JAPA
Date:May 1, 2002
Words:1893
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