Parotid Gland Oncocytosis: CT Findings with Histopathologic Correlation

Abstract

SUMMARY:Oncocytic neoplasms result from metabolically altered cells that accumulate abundant mitochondria within their cytoplasm by oncocytic metaplasia. In this report, the CT findings are described and correlated with the histopathologic features of a case of oncocytoma involving the parotid gland that arose in a background of nodular oncocytic hyperplasia. When imaging demonstrates multiple small nodules in the parotid gland with a large, solid, or cystic mass, the diagnosis of oncocytic neoplasia should be considered.O ncocytic neoplasms result from metabolically altered cells that accumulate abundant mitochondria within their cytoplasm to form oncocytes by the process of oncocytic metaplasia. These neoplasms are found rarely in the parotid gland and account for Ͻ1% of salivary gland tumors. However, the finding of oncocytic metaplasia is extremely common and occurs in a multitude of organs, including the thyroid gland, parathyroid glands, and kidneys, in addition to salivary glands.In the parotid gland, oncocytic metaplasia arises along a spectrum of related conditions, including oncocytic hyperplasia, benign oncocytoma, and, rarely, oncocytic carcinoma. Oncocytic hyperplasia may be found in microscopic foci or multiple macroscopic nodules, known as nodular oncocytic hyperplasia. Oncocytoma is a benign tumor comprising bland oncocytes, usually presenting as a single nodule.To our knowledge, the imaging findings of oncocytic metaplasia of the salivary gland have only limited description in the literature. We present the CT and histopathologic findings of a case of oncocytoma arising in a background of oncocytic hyperplasia of the parotid gland. Case ReportA 61-year-old white man presented with a 3-year history of painless right parotid gland fullness. One week prior, he developed sudden constant dull aching pain radiating from the right parotid region. Physical examination revealed diffuse enlargement of the parotid gland with a soft nontender right retromandibular mass. Intraoral examination revealed bulging of the right oropharynx. No facial nerve dysfunction or cervical lymphadenopathy was found.CT revealed enlargement of the superficial lobe and loss of normal architecture of the right parotid gland. Multiple solid masses, most Ͻ1 cm in diameter, were seen within the gland. A retromandibular mass demonstrated cystic necrosis with a rim of peripheral enhancement (Fig 1A). The largest mass, in the tail of the parotid gland, measured 1.6 cm and was suggestive of a metastatic lymph node ( Fig 1B). A more focal well-defined mildly enhancing tumor was also seen within the deep lobe of the parotid gland, measuring 4.2 cm transversely and 2.6 cm anteroposteriorly (Fig 1A, black arrow). The tumor extended from just below the skull base to the angle of the mandible.Total parotidectomy was performed by a combined transparotidsubmandibular approach, sparing the facial nerve. Multiple enlarged well-circumscribed ovoid masses were found in the periparotid region and parotid tail and appeared as lymph nodes. Frozen-se...

CT Features of Parotid Gland Oncocytomas: A Study of 10 Cases and Literature Review

“…Patients typically present with a solitary slow-growing painless parotid mass, 3,4,6,8,9,16,19,20 similar to that observed in our series. All 10 patients in our series were adults in their fifth to eighth decades with a female preponderance.…”

“…15,16,[19][20][21] The reports on MR imaging of parotid oncocytomas describe these tumors as demonstrating T1 and T2 hypointensity with homogeneous contrast enhancement.…”

“…4,[7][8][9][13][14][15][16] The parotid gland is the most commonly involved salivary gland, accounting for 78%-84% of salivary gland oncocytomas.…”

“…2,17,18 To the authors' knowledge, there is limited description of the CT imaging features of parotid gland oncocytomas in the published literature, apart from a few case reports. 15,16,[19][20][21] Because the surgical resection of parotid tumors is generally the treatment of choice and allows histopathologic confirmation, the identification of specific CT imaging features suggestive of benign parotid oncocytomas will become helpful in terms of simply managing the patient expectantly when certain clinical scenarios arise-for example, if the patient declines surgical intervention, when patient factors such as age and multiple comorbidities preclude surgical resection, or when biopsy results are not diagnostic. In this study, we describe the CT features of 10 histopathologically proved cases of parotid oncocytomas, the largest imaging series in the published literature, to our knowledge.…”

Parotid gland oncocytoma: a case report

“…Diagnosis is assisted by CT and/or magnetic resonance imaging (MRI) of the neck, although histopathologic confirmation is necessary. However, in a recent report, CT findings were correlated to histopathologic features [5]. Pathologically, oncocytoma is described as a well circumscribed mass, composed of layers of oncocytes (small round nucleus, micro-granular, eosinophilic cytoplasm).…”