Squamous cell carcinoma of the accessory parotid gland.

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An 85-year-old man presented with a persistent right accessory parotid gland carcinoma after surgical resection and radiotherapy (figure 1). The patient had been initially diagnosed by fine-needle aspiration as having a moderately to well-differentiated keratinizing squamous cell carcinoma of the right accessory parotid gland. He had been initially treated with a right total parotidectomy and resection of the right accessory gland tumor with facial nerve preservation.

At the time of resection, the superficial lobe of the parotid gland showed signs of sialadenitis but no sign of malignancy. However, the deep lobe was positive for foci of carcinoma with no intraparotid nodal disease. The accessory tumor measured approximately 4 cm, and it extended into fatty soft tissues focally at two resection margins.

The patient deferred further surgery and was treated with intensity-modulated radiotherapy. He received 6,800 cGy to the tumor bed and 5,400 cGy to the ipsilateral cervical nodal chain. Toward the end of radiotherapy, a nodule developed within the radiation field. The nodule was biopsied and found to be consistent with persistent squamous cell carcinoma. The tumor had ulcerated through the overlying facial skin, and it extended to the posterior maxillary tuberosity. The patient underwent a whole-body computed tomography/positron-emission tomography (CT/PET) fusion scan, which revealed the presence of a hypermetabolic 4- to 5-cm lesion just caudal to the right zygomatic arch (figure 2). No other area of hypermetabolic activity was noted.

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The patient underwent salvage surgery, which included a full-thickness composite facial resection. The surgery left a large facial-oral defect, which was reconstructed with a pectoralis major myocutaneous flap (figure 3). The oral cavity was allowed to remucosalize (figure 4). At the 3-year follow-up, the patient was disease-free by examination and CT/PET imaging (figure 5).

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Accessory parotid glands are present in approximately 21% of the population. (1) These small flat structures were once considered to be mere extensions of the main parotid gland, but it is now known that they are independent glandular units with respect to their function and anatomic location. Accessory parotid glands are associated with a higher rate of malignant tumors (26 to 50%) than are the main parotid glands (18 to 20%). (2) It has been postulated that this higher rate of malignancy is attributable to the histology of the accessory parotid gland. In contrast to the predominant serous composition of the main parotid gland, the accessory parotid gland is made up of a fairly equal percentage of mucinous and serous acinar units, as is the submandibular gland. (3) The lack of anatomic barriers to tumor extension predisposes these tumors to significant soft-tissue infiltration.

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References

(1.) Frommer J. The human accessory parotid gland: Its incidence, nature, and significance. Oral Surg Oral Med Oral Pathol 1977;43(5): 671-6.

(2.) Perzik SL, White IL. Surgical management of preauricular tumors of the accessory parotid apparatus. Am J Surg 1966;112(4):498-503.

(3.) Toh H, Kodama J, Fukuda J, et al. Incidence and histology of human accessory parotid glands. Anat Rec 1993;236(3):586-90.

Ryan F. Osborne, MD, FACS 

From the Osborne Head and Neck Institute, Los Angeles.