Bilateral multinodular oncocytomas of the parotid arising in a background of bilateral oncocytic nodular hyperplasia.
Oncocytic tumors of the major salivary glands are rare, accounting for less than 1% of all salivary gland tumors. When they do occur, these neoplasms typically present as solitary nodules that affect only one major salivary gland, usually the parotid. Multiple bilateral multinodular tumors are rare. We report the case of a 53-year-old woman with a case of synchronous multiple bilateral multinodular oncocytomas that arose in a background of bilateral oncocytic nodular hyperplasia in the parotid glands. The patient underwent superficial parotid resections, and at the 4-year follow-up, she exhibited no evidence of recurrence.
Oncocytic salivary gland tumors are rare, accounting for fewer than 1% of all salivary gland neoplasms. (l,2) Although McFarland (3) is credited with describing the first oncocytic salivary gland tumor in 1927, pioneering work by Hamperl (4) published in 1931 led the way to recognizing oncocytic changes, both hyperplastic and neoplastic. Hamperl's subsequent report of 46 such lesions, which was published in 1962, was the first comprehensive review of oncocytic neoplasms. (5)
Oncocytomas usually present as solitary, and hence unilateral, lesions. To date, only about 20 cases of bilateral tumors have been reported in the world literature? (1,6-10) These tumors presented as synchronous or metachronous lesions of the parotid glands to the exclusion of the other major salivary glands.
In this article, we report a rare case of synchronous multiple bilateral multinodular parotid oncocytomas that arose in a background of bilateral oncocytic nodular hyperplasia. We also discuss the features that characterize oncocytomas and nodular hyperplasia based on our review of the existing limited literature on bilateral oncocytomas.
A 53-year-old white woman presented to our outpatient clinic with a 5-year history of a gradual bilateral nodular enlargement of her parotid glands. Her primary concern was the disfiguring effect of the nodularity, particularly on the left side of her face. She reported no pain, and she exhibited no signs of facial nerve weakness. Her medical, surgical, family, and social history was unremarkable, and all her laboratory tests, including a screen for human immunodeficiency virus, were negative.
Magnetic resonance imaging (MRI) of the parotid areas had been obtained earlier by the referring physician. It showed multiple bilateral nonenhancing parotid masses that demonstrated variable intensity on T2 weighting (figure 1). Physical examination revealed that the nodules were firm and nontender, and they were indeed more prominent on the left. The patient's neck was free of lymphadenopathy.
Routine posteroanterior and lateral chest x-rays were normal. Fine-needle aspiration was performed at multiple nodular sites; cytology consistently demonstrated a uniform oncocytic population of cells with no significant cytologic atypia. This finding was consistent with a bilateral oncocytic lesion (differential diagnosis: hyperplastic vs. neoplastic lesion). The patient underwent superficial parotid resections, and the parotid bed was reconstructed with AlloDerm. The patient recovered from surgery without facial nerve weakness or any other complication.
Gross examination of the resected parotid tissues revealed fragmented nodular pieces of soft brown and tan tissue. Serial sectioning of the tissue fragments revealed discrete round nodules that ranged in size from 0.2 to 2.5 cm (figure 2). Each nodule was pink-tan to brown throughout. No hemorrhage or necrosis was evident, but macrocystic change was noted in one of the larger nodules.
Microscopic examination of the tissue revealed multiple loci of oncocytic cell aggregates in nodule formations scattered among normal parotid tissue (figure 3). The oncocytic cells, 10 to 15 pm in diameter, showed the usual morphology: an abundant, finely granular eosinophilic cytoplasm and centrally placed round nuclei with prominent nucleoli and slight nuclear pleomorphism (figure 4, A). Some of the cells exhibited clear-cell morphology, although the location of the clear-cell nuclei was more peripheral (figure 4, B) than what is typically seen in oncocytic morphology, in which the nuclei are centrally placed. The cells were arranged in solid, organoid, and trabecular patterns; thin fibrous stroma and blood vessels separated the trabecular and 0rganoid forms. Many of the nodule formations blended imperceptibly with the surrounding glandular tissue, with no apparent circumferential or intervening fibrous tissue formation; these formations had a more irregular outline (figure 4, C). The larger, more dominant nodules were contained in well-defined, well-circumscribed fibrous capsules that separated them from the surrounding tissues (figure 4, D). No entrapped normal parotid gland elements were observed. It is interesting that these encapsulated nodules also exhibited more of a solid pattern of growth and occasional cyst formation. It thus became evident that there were two patterns of growth--hyperplastic and neoplastic. The hyperplastic pattern was characterized by the unencapsulated nodular growth pattern and irregular outline. The neoplastic pattern was characterized by the well-encapsulated, round, solid nodules.
No evidence of malignant transformation was evident. On the basis of the cytologic features, we made a diagnosis of multiple bilateral multinodular oncocytomas of the parotid glands arising in a background of multifocal nodular oncocytic hyperplasia.
The patient was followed in our outpatient clinic, and at 4 years postoperatively, she exhibited no evidence of recurrence.
Cells with oncocytic morphology have been described in many organ systems throughout the body (e.g., kidney, thyroid, and breast) since they were first observed by Schaffer in 1897 in tissues from the upper aerodigestive tract. (11) Within the salivary glands, the appearance of these cells in focal metaplastic, hyperplastic, or neoplastic oncocytic processes is usually related to increasing age. They are seen most often in the sixth and seventh decades of life; rarely are they encountered in patients younger than 50 years. (4,12,13)
It is not entirely clear whether the development of oncocytic neoplasia (benign oncocytoma/oncocytic carcinomas) is a discrete independent event or if it occurs along a continuum of oncocytic metaplasia/hyperplasia that ultimately leads to a neoplastic change. As is the case with many other well-researched pathologic events, it is reasonable to theorize that both scenarios maybe in play. More research is certainly needed to clarify this point.
[FIGURE 1 OMITTED]
Etiologic factors that may trigger neoplastic change include radiation exposure, metabolic mitochondrial defects, and genetic predispositions. In this regard, Brandwein and Huvos (1) found a history of radiation exposure in some of their cases, and Becker et al (14) described an age-dependent intracellular metabolic defect associated with mitochon driopathy as an explanation for the development of oncocytosis in 2 of their cases. However, the pathogenesis of the proposed continuum (metaplasia/hyperplasia/tumoral change) remains largely undefined.
[FIGURE 2 OMITTED]
Most investigators agree with the World Health Organization's classification of oncocytic lesions. (15) The WHO groups these tumors into three distinct categories: diffuse oncocytosis, multifocal nodular oncocytic hyperplasia (MNOH), and oncocytomas (benign and malignant). (15) However, the differentiation between hyperplasia and oncocytoma has been the subject of much debate. Some investigators have discussed the possibility that a benign oncocytoma may not be a true neoplasm at all, but rather an encapsulated hyperplastic variant. (8,16,17) Others, including the authors of this article, do not share that view; we consider oncocytomas and nodular hyperplasia to be two distinct pathologic entities. Our position is supported by the results of a study by Palmer et al, who reviewed 26 oncocytic salivary gland lesions. (13) They found that the median age for the development of MNOH and oncocytoma together (65 yr) was higher than that for MNOH alone (42 yr). This finding lends more support to the theory of progressive tumoral change in a hyperplastic process. Brandwein and Huvos described it best when they wrote that the development of oncocytomas in a background of nodular oncocytic hyperplasia is analogous to the development of a thyroid adenoma in a background of adenomatous thyroid goiter.
Most authors do agree that the microscopic differentiation between a hyperplastic oncocytic nodule and a tumoral nodule (benign oncocytoma) is based primarily on the presence or absence of a well-defined fibrous capsule that encompasses the tumor completely or at least partially and separates it from the surrounding tissues. Hyperplastic nodules usually do not feature this encapsulation; they have an irregular outline that blends into the circumferential tissues with no fibrous barrier, and they tend to be lobular rather than lobar. (15-17) Also, parotid oncocytomas tend to be easily detectable clinically because their size typically ranges from 1 to 7 cm, which is larger than most of the nodules seen in MNOH. As a result, patients are more likely to seek medical evaluation.
The parotid gland is by far the most common site of salivary gland oncocytomas (85 to 90% of cases). (15,16) These neoplasms usually present as a single mass that involves only one parotid gland. Bilateral parotid gland involvement by oncocytomas is rare. Indeed, bilateral parotid tumors of any kind are unusual; Warthin's tumor is the most common. To date, bilateral oncocytomas have been seen only in the parotid gland. (1,6-10) Gnepp et al, in a review of bilateral salivary gland neoplasms published in 1989, documented 12 cases of bilateral oncocytomas in the world literature and found that they occurred as synchronous or metachronous events. (6) Some authors also reported the multinodular fashion by which some oncocytomas present and warned against interpreting the multinodularity as a sign of malignancy. (18,19)
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In the report by Brandwein and Huvos, who studied 68 oncocytic lesions of the major salivary glands, the incidence of bilateral oncocytomas was 7%. (1) These authors found that bilateral presentations correlated with significant clear-cell change. Ellis reviewed 10 cases of clear-cell oncocytomas and found that clear-cell change occurred secondary to glycogen accumulation; however, mitochondria were still the preponderant intracytoplasmic organelle, as they are in typical oncocytomas. (20)
Our patient, in her sixth decade of life, sought medical attention after noticing the disfiguring facial effect caused by the presence of bilateral parotid region nodularity. Surgical excision followed by histologic evaluation revealed a diffuse bilateral nodular oncocytic hyperplasia of the parotid gland together with bilateral multinodular oncocytomas that exhibited clear-cell features at focal areas. We have described this unusual case in an effort to stress to clinicians and pathologists alike the importance of considering this rare entity in the differential diagnosis of bilateral nodular parotid gland enlargement. This is particularly important when the treating physician and the pathologist are considering a malignant process on the basis of the appearance of bilateral and multicentric tumor growths.
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From the Department of Pathology (Dr. Hyde and Dr. Said) and the Department of Otolaryngology (Dr. Takashima and Dr. Dodson), University of Colorado Health Science Center, Denver.
Corresponding author: Sherif Said, MD, Department of Pathology, University of Colorado Health Sciences Center at Fitzsimmons, Mail Stop 8104, PO Box 8511, Aurora, CO 80045. Phone: (303) 724-0154; fax: (303) 714-3712; e-mail: firstname.lastname@example.org
Jason Hyde, MD; Masayoshi Takashima, MD; Brennan Dodson, MD; Sherif Said, MD, PhD
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|Author:||Hyde, Jason; Takashima, Masayoshi; Dodson, Brennan; Said, Sherif|
|Publication:||Ear, Nose and Throat Journal|
|Article Type:||Disease/Disorder overview|
|Date:||Jan 1, 2008|
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