Adenoid Cystic Carcinoma of Accessory Parotid Gland: A Case Report

Adenoid Cystic Carcinoma of Accessory Parotid Gland: A Case Report

SURGICAL ONOCOLOGY AND RECONSTRUCTION Adenoid Cystic Carcinoma of Accessory Parotid Gland: A Case Report Somdipto Das, MDS,* Umanath K. Nayak, MS,y R...

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SURGICAL ONOCOLOGY AND RECONSTRUCTION

Adenoid Cystic Carcinoma of Accessory Parotid Gland: A Case Report Somdipto Das, MDS,* Umanath K. Nayak, MS,y Rahul Buggavetti, MS, MCh,z and Shobana Sekhar, MDSx The accessory parotid gland is salivary gland tissue separated from the main gland at a variable distance. This gland is histologically similar to the main gland, but has a higher incidence of malignant neoplasms than the main gland. Regarding the various malignant neoplasms, studies have shown higher incidences of mucoepidermoid carcinoma, with less than 2% being adenoid cystic carcinoma. We present a case of swelling in the midcheek region that, after clinical examination, was diagnosed as a case of neoplasm of the accessory parotid gland. On the basis of auxiliary investigations including intraoperative frozen section, it was concluded that it was adenoid cystic carcinoma, grade I, and after wide surgical resection, the tumor was removed without undergoing superficial parotidectomy. The patient received postoperative radiotherapy (RT) and was followed for 14 months without any recurrence or substantial facial asymmetry. Ó 2016 American Association of Oral and Maxillofacial Surgeons J Oral Maxillofac Surg -:1.e1-1.e5, 2016 The accessory parotid glands are located anterior to and separate from the main parotid gland. The anterior extension that is attached to the parotid is termed the ‘‘facial process’’ and not the ‘‘accessory parotid gland.’’1 Midcheek region swellings are difficult to diagnose clinically and can range from reactive lymphadenopathy to neoplasms of normal anatomic structures in the vicinity, such as hemangiomas, neurofibromas, schwannomas, skin adnexal tumors, and even neoplasms of accessory structures like an accessory parotid gland. We report a case that presented to us as a midcheek swelling arising from the accessory parotid gland and was diagnosed histologically as adenoid cystic carcinoma, grade I. The case is reported in view of the rarity of the condition and the challenges it poses in its diagnosis and surgical approach.

A 29-year-old male patient came to our outpatient department with the chief complaint of swelling over the right side of the cheek of 2 months’ duration. The swelling was gradually increasing in size without

any pain in the region. There was no relevant history and no deleterious habits reported by the patient. On local examination, a 2  2–cm firm, mobile, spherical swelling with well-defined edges was located over the anterior edge of the masseter muscle. The swelling became prominent on clenching of the teeth, suggesting a superficial location of the swelling with respect to the masseter muscle. No facial nerve paresis was detected in any of the terminal branches of the facial nerve. There also was no deviation of the corner of the mouth of the patient and no pulsation felt or bruit auscultated over the swelling. Finally, there was no fixity of the swelling to the overlying skin (Fig 1). Fine-needle aspiration cytology (FNAC) was performed, but inconclusive findings were reported. The ultrasonography findings indicated a hypoechoic mass suggestive of a cystic consistency. Computed tomography (CT) scan with a soft tissue window showed, on axial and coronal views, a wellcircumscribed hypodense mass located superficial to the masseter muscle and anterior to the main parotid gland (Fig 2). The patient was informed about the probable lesion and the risk of damage to the branches of the facial

Received from Department of Head and Neck Surgical Oncology,

Jubilee Hills, Hyderabad, Telangana, India; e-mail: [email protected]

Apollo Cancer Hospital, Hyderabad, India. *Fellow.

gmail.com Received October 16 2015

Report of Case

yFellow (AHNS) and Department Head.

Accepted January 5 2016

zConsultant.

Ó 2016 American Association of Oral and Maxillofacial Surgeons

xRegistrar.

0278-2391/16/00027-6

Address correspondence and reprint requests to Dr Das: Depart-

http://dx.doi.org/10.1016/j.joms.2016.01.012

ment of Head and Neck Surgical Oncology, Apollo Cancer Hospital,

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FIGURE 1. Midcheek swelling marked on the patient. Das et al. Accessory Parotid Gland Tumor. J Oral Maxillofac Surg 2016.

FIGURE 3. Intraoperative photograph showing the accessory parotid gland tumor anterior to the superficial musculo aponeurotic system layer and encircling the Stensen duct of the parotid. Das et al. Accessory Parotid Gland Tumor. J Oral Maxillofac Surg 2016.

Postoperatively, the patient recovered well without any weakness of facial nerve function. On final histopathologic analysis, sections showed

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nerve during surgery, and written consent was obtained for surgery following the Declaration of Helsinki guidelines. A modified Blair incision was used to expose the swelling. The buccal branch of the facial nerve was identified anterior to the parotid gland and traced. The tumor was found to be lying between the buccal and zygomatic branches of the facial nerve and encasing the Stensen duct (Fig 3). The tumor was dissected out completely (Fig 4) after ligation and excision of the Stensen duct on that side without any anastomosis of the segmental duct ends.

FIGURE 2. Computed tomography scan showing a hypodense well-circumscribed mass located superficial to the masseter muscle on the right side of the face.

FIGURE 4. Accessory parotid gland tumor after excision.

Das et al. Accessory Parotid Gland Tumor. J Oral Maxillofac Surg 2016.

Das et al. Accessory Parotid Gland Tumor. J Oral Maxillofac Surg 2016.

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FIGURE 5. A, Histopathologic picture showing a fairly well-circumscribed tumor composed of anastomosing cords of basaloid cells with intervening hyaline eosinophilic material (Hematoxylin and Eosin stain, original magnification 20). B, Histopathologic picture showing basaloid cells with coarse chromatin and scanty cytoplasm (Hematoxylin and Eosin stain, original magnification 40). Das et al. Accessory Parotid Gland Tumor. J Oral Maxillofac Surg 2016.

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a fairly well-circumscribed tumor composed of anastomosing cords of basaloid cells with coarse chromatin and scanty cytoplasm. Intervening hyaline eosinophilic material was seen with few mitotic figures. No necrosis or solid areas were seen. The surgical margin was negative for tumor involvement, and no perineural infiltration was seen (Fig 5). The diagnosis was consistent with adenoid cystic carcinoma, grade I. The patient received postoperative radiotherapy (RT) to a dose of 60 Gy to the area of the tumor bed and course of the facial nerve to its exit from the skull base. He was followed-up for a period of 14 months

FIGURE 6. Postoperative photograph of the patient showing good facial symmetry 14 months after surgery and postoperative radiotherapy. Das et al. Accessory Parotid Gland Tumor. J Oral Maxillofac Surg 2016.

after surgery and postoperative RT and was reported to be free of disease (Fig 6).

Discussion The accessory parotid gland is histologically a mass of salivary gland tissue located anterior to and separate from the main parotid gland. It has been found to be present in 21%1 to as high as 56%2 of the general population. The average distance of the accessory parotid gland from the main gland was found to be 6 mm, and it sometimes has even been reported to be located anterior to the masseter muscle on the buccal pad of fat.1 Clinically, accessory parotid gland tumors present as a swelling in the midcheek portion without any pain or tenderness. The differential diagnosis can include various neoplasms occurring in this region and can range from reactive lymphadenopathy to neoplasms of the nerve fibers, such as a neurofibroma or schwannoma; neoplasms of the blood vessels, such as a hemangioma; or lipoma of the buccal fat pad. It also can include simple inclusion cysts caused by trauma to the region. Accessory parotid gland tumors are located in the middle-third region of a line drawn from the tragus of the ear to the midpoint of a line from the ala of the nose to the vermillion border of the upper lip.3 Investigations of choice for tumors of the accessory parotid glands include FNAC, ultrasonography, CT scan, CT scan with a sialogram, magnetic resonance imaging (MRI), MRI with a sialogram, and positron emission tomography in cases of recurrent lesions or distant metastasis. FNAC is often the investigation of choice in diagnosing swelling because it is a straightforward and fast technique, but the findings can

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sometimes be inconclusive; moreover, FNAC has a theoretical risk of seeding malignant cells deep into the gland in malignant neoplasms.4 A CT scan or a CT scan along with a sialogram helps to better delineate the anatomic relationships, thus helping to estimate the location of the tumor with respect to the muscle and the main parotid gland.5 MRI with contrast is considered an ideal imaging modality4 because it is highly sensitive for soft tissue lesions and for detecting perineural invasion of the facial nerve by a tumor. However, because no facial nerve paresis was reported or clinically detected in our patient and he initially reported with a contrast CT scan, we believed that further imaging, such as MRI, was unlikely to uncover any additional information beyond that already provided by contrast CT. The incidence of neoplasms in the accessory parotid glands has ranged from 1% in a series of 2,291 parotid tumors6 to 7.7% in another series of 591 parotid tumors.3 The incidence of malignant accessory parotid tumors also has varied among studies, from as high as 33.3%7 to 50%6 in some to as low as 25% in others.3,8 However, all studies concluded that although the incidence of neoplasms is much lower compared with the main parotid gland (18.5%),2 the chances of malignancy are certainly higher among such neoplasms compared with the main parotid gland. Among the benign and malignant neoplasms of the accessory parotid glands, pleomorphic adenoma is the most common benign neoplasm and low-grade mucoepidermoid carcinoma is the most common malignant neoplasm.4 Some studies have reported that acinic cell carcinoma is the most common malignant neoplasm.8 The incidence of adenoid cystic carcinoma in the accessory parotid glands has ranged from 3.6% in a series of 167 cases7 to as low as 2% in a series of 150 cases.8 Surgery is the primary method of management for all salivary gland tumors, and accessory parotid tumors are no exception to this. Different approaches for addressing accessory parotid tumors are reported in the literature, including a midcheek incision, an intraoral approach, a facelift approach, and a modified Blair incision with or without a superficial parotidectomy. Each approach has certain advantages and disadvantages. The midcheek incision has a high propensity of causing damage to the branches of the facial nerve, especially the buccal branch,9 because no formal identification of the nerve branches is performed. The intraoral incision is only propagated for tumors located medial to the masseter muscle and, similarly, may result in damage to the buccal branch if the nerve is in proximity to the tumor. The modified Blair incision is the most widely used approach, and it was used in our case.

Adenoid cystic carcinoma of the salivary gland is classified into 3 grades, depending on its histologic pattern and behavior of the tumor, by the MD Anderson Cancer Center and Batsakis et al.10 Grade I adenoid cystic carcinoma is a low-grade tumor with a 15-year survival rate of 39%, as compared with 20% and only 5% for grade II and grade III, respectively. Surgery with adequate margins is the mainstay of treatment for all grades of adenoid cystic carcinoma. RT or chemotherapy and RT11,12 also is used as an adjuvant therapy for intermediate- and higher-grade tumors or tumors with adverse features (positive margins, perineural invasion). With the accessory parotid gland being away from the main parotid gland, malignant neoplasms involving accessory parotid gland require excision with adequate margins and superficial parotidectomy is not deemed necessary for management. The absence of facial nerve paresis clinically suggests the absence of perineural invasion; thus the nerve branches also are preserved.13 Although superficial parotidectomy has been suggested by a few studies, both for ease of identification of the nerve branches and for obtaining margins in malignant tumors,2,5,14 we strongly believe that wide excision of the tumor with adjuvant RT is a better treatment modality, thus maintaining facial symmetry in younger individuals. Because the tumor was adherent to the Stensen duct, the duct was ligated and excised. Tumors of the accessory parotid glands are extremely rare, and few reports are found in the literature. Although the incidence of malignancy in the accessory parotid glands is higher, adenoid cystic carcinoma is relatively uncommon. On the basis of the history and clinical location of the tumor, neoplasms of the accessory parotid glands should be considered as a diagnosis after ruling out other common pathologies. Surgical management involves wider exposure and excision of the tumor with wide margins, followed by adjuvant RT or chemotherapy and RT. This, in turn, preserves the facial symmetry in the postoperative period in contrast to superficial parotidectomy, which can cause facial asymmetry and higher chances of facial nerve damage.

References 1. Frommer J: The human accessory parotid gland: Its incidence, nature, and significance. Oral Surg Oral Med Oral Pathol 43: 671, 1977 2. Toh H, Kodama J, Fukuda J, et al: Incidence and histology of human accessory parotid glands. Anat Rec 23:586, 1993 3. Perzik SL, White IL: Surgical management of preauricular tumors of the accessory parotid apparatus. Am J Surg 112:498, 1966 4. De Riu G, Meloni SM, Massarelli O, Tullio A: Management of midcheek masses and tumors of the accessory parotid gland. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 111:e5, 2011 5. Kronenberg J, Horowits A, Creter D: Pleomorphic adenoma arising in accessory salivary tissue with constriction of Stensen’s duct. J Laryngol Otol 102:382, 1988

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DAS ET AL 6. Johnson FE, Spiro RH: Tumors arising in accessory parotid tissue. Am J Surg 138:576, 1979 7. Luksic I, Suton P, Rogic M, Dokuzovic S: Accessory parotid gland tumours: 24 years of clinical experience. Int J Oral Maxillofac Surg 41:1453, 2012 8. Yang X, Ji T, Wang LZ, et al: Clinical management of masses arising from the accessory parotid gland. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 112:290, 2011 9. Rodino W, Shaha AR: Surgical management of accessory parotid tumors. J Surg Oncol 54:153, 1993 10. Batsakis JG, Luna MA, el-Naggar A: Histopathologic grading of salivary gland neoplasms: III. Adenoid cystic carcinomas. Ann Otol Rhinol Laryngol 99:1007, 1990

11. Ross PJ, Teoh EM, A’Hern RP, et al: Epirubicin, cisplatin and protracted venous infusion 5-Fluorouracil chemotherapy for advanced salivary adenoid cystic carcinoma. Clin Oncol (R Coll Radiol) 21:311, 2009 12. Vermorken JB, Verweij J, de Mulder PH, et al: Epirubicin in patients with advanced or recurrent adenoid cystic carcinoma of the head and neck: A phase II study of the EORTC Head and Neck Cancer Cooperative Group. Ann Oncol 4:785, 1993 13. Vander Poorten V, Bradley PJ, Takes RP, et al: Diagnosis and management of parotid carcinoma with a special focus on recent advances in molecular biology. Head Neck 34:429, 2012 14. Polayes IM, Rankow RM: Cysts, masses, and tumors of the accessory parotid gland. Plast Reconstr Surg 64:17, 1979

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