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Unusual parapharyngeal acinic cell carcinoma.

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Acinic cell neoplasms are rare in the major salivary glands, and they are even more rare in the minor salivary glands and other sites. (1-3) We describe an unusual presentation of a parapharyngeal acinic cell carcinoma (ACC) that arose from a minor salivary gland.

The patient was a 51-year-old man who presented with a progressively enlarging, left-sided parapharyngeal mass. Computed tomography (CT) demonstrated a circumscribed, low-density, peripherally enhancing mass on the left (figure 1). CT also showed adjacent multilevel, nonspecific, subcentimeter lymph nodes. The mass was completely excised. Grossly, the specimen was a pink-maroon rubbery mass measuring 4.5 x 4.0 x 2.0 cm. Sectioning revealed a cystic cut surface with a tan-pink hemorrhagic and fibrous wall.

Microscopically, the lesion consisted of a fibrous walled pseudocyst with an infiltrative mass of cells arranged in nests and microcysts (figure 2). The cells featured granular basophilic cytoplasm and an eccentric nucleus. Mild nuclear pleomorphism was seen, and the mitotic activity was low. No evidence of metastatic lymphadenopathy was present.

On clinical and imaging follow-up at 6 months, the patient remained stable.

Salivary gland carcinomas represent 0.3 to 0.9% of all cancers in the United States; of these, 6 to 10% are ACCs. (1) ACCs are most common in whites and in women, and the average age at onset is 52 years. (4) In 80% of cases, these slowly growing malignant tumors occur in the parotid gland and are accompanied by pain and/or tenderness. (3) They are less common than mucoepidermoid carcinomas, adenoid cystic carcinomas, and carcinomas ex pleomorphic adenoma. ACCs are derived from serous acinar cells; pathologic evaluation will show basophilic cytoplasm. There are four subtypes of ACC: solid, microcystic, papillary-cystic, and follicular. (1,2) These four subtypes can occur together in any combination.

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Most ACCs develop within the parotid gland, and most have the potential to invade the facial nerve. Other reported sites include the palate (as many as 15% of cases), the submandibular gland (4%), and the sublingual gland (1%). (3) It is interesting that this tumor is the most common bilateral malignant salivary gland neoplasm. Its bilateral presentation is not nearly as common as the bilateral presentation of benign tumors such as Warthin tumor and pleomorphic adenomas. (3)

ACCs have an unpredictable course. Local recurrence has been reported, as has occasional distant metastasis to the lungs and the bones via hematogenous spread and metastasis to regional lymph nodes. (5) Mortality at 5 years is usually less than 10%, but by 20 years, it is as high as 50%. (2)

References

(1.) Yokoyama M, Nomura Y, Semba T. Acinic cell carcinoma of the parapharyngeal space: Case report. Head Neck 1993;15(1):67-9.

(2.) Vinod S, George A, Sunil S, James M. Acinic cell carcinoma of palate a rare presentation. J Oral Maxillofac Pathol 2011;2(1):137-41.

(3.) Thompson LD. Salivary gland acinic cell carcinoma. Ear Nose Throat J 2010;89(11):530-2.

(4.) Kim SA, Mathog RH. Acinic cell carcinoma of the parotid gland: A 15-year review limited to a single surgeon at a single institution. Ear Nose Throat J 2005;84(9):597-602.

(5.) Ota Y, Arai T, Yamazaki H, et al. Acinic cell carcinoma of the sublingual gland accompanied by bone formation. Tokai J Exp Clin Med 2001;26(4 6):127-30.

Jeremy Nguyen, MD; Enrique Palacios, MD, FACR; Elorice Horam, MD; Harold Neitzschman, MD, FACR

From the Department of Radiology, Tulane University Hospital and Clinics, New Orleans.
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Title Annotation:IMAGING CLINIC
Author:Nguyen, Jeremy; Palacios, Enrique; Horam, Elorice; Neitzschman, Harold
Publication:Ear, Nose and Throat Journal
Article Type:Case study
Date:Feb 1, 2012
Words:583
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