Abstract
Accessory parotid gland (APG) is a small salivary gland tissue ranging from 0.5 to 1 cm diameter in size, located almost 7 mm anterior to the main parotid gland. APG is a common anatomical variant, but accessory parotid gland tumors are very rare, accounting for only 1%–7.7% of all parotid gland tumors. We present a case of adenoid cystic carcinoma involving accessory parotid gland, a very rare condition with only, to the best of our knowledge, other 7 cases described in literature. Surgical excision was performed and eventful postoperative recovery, without severe surgical complications and no signs of recurrence at 12 months of follow-up was obtained, with a good cosmetic result. An extensive review of the literature has been performed and the results are presented in order to establish a correct diagnostic-therapeutic protocol for these oncologic patients.
Highlights
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Accessory parotid gland (APG) is a common anatomical variant, with a frequency in autopsy studies ranging from 21% to 56%.
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Tumors of APG are very rare, only 1%–7.7% of all parotid gland tumors, with a malignancy rate from 26% to 52%.
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We present a case of adenoid cystic carcinoma of APG, described, to the best of our knowledge, other seven time in literature.
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Adenoid cystic carcinoma is characterized for three histopathological patterns: tubular, cribriform and solid.
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Complete surgical excision is necessary, such as a strict follow-up to rule out local recurrence.
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INTRODUCTION
Accessory parotid gland (APG) is a small salivary gland tissue ranging from 0.5 to 1 cm diameter in size, located almost 7 mm anterior to the main parotid gland. APG is a common anatomical variant, with a frequency in autopsy studies ranging from 21% to 56% [ , ].
APG tumors are very rare, accounting for only 1%–7.7% of all parotid gland tumors, with a malignancy rate ranging from 26% to 52% compared to the 18.5% malignancy rate for tumors of the main parotid gland [ , ]. According to the data extracted from the literature, adenoid cystic carcinoma in the accessory parotid glands has an incidence of 1.9% [ ]. We report a case of a patient who presented to us with a mid-cheek swelling arising from the accessory parotid gland, and diagnosed as adenoid cystic carcinoma. To the best of our knowledge, this is the seventh case reported in literature.
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PRESENTATION of case
In November 2018, a 52-year-old man was presented to Maxillo-Facial Unit of Federico II University, Naples, Italy with a painless nodule in the right mid-cheek region. Accurate anamnesis revealed that the mass had been increasing slowly in size over the last 8 months. Initial imaging studies included ultrasound scanning, followed by fine‐needle aspiration cytology (FNAC) biopsy and CT scans. On clinical examination he presented an oval, firm and slightly movable, subcutaneous mass in the right mid-cheek region, measuring 2,5 × 1,5 cm with elastic consistency ( Fig. 1 ). All cranial nerves were intact and no cervical adenopathy was palpated. Ultrasound scanning revealed a hypodense mass of 23 × 14 mm in size located under the skin, around the anterior edge of the masseter muscle, originating from the right accessory parotid gland. The patient underwent a first fine needle aspiration cytology (FNAC) examination that showed an inconclusive diagnosis, and a second one that instead showed “mucoid material with epithelial elements through acinar cell aggregates without atypic cells compatible with adenomatous proliferation”. The computed tomography scans ( Fig. 2 A and B) confirmed a cystic nodule anterior to the parotid gland, non-vascularized, measuring 22 × 12 × 15 mm, with no pathologic cervical lymphadenopathy.
The patient underwent a superficial parotidectomy. The lesion was handled through a “facelift” incision, achieving a good exposure for the accessory lobe. The tumor was dissected out completely, together with superficial lobe of parotid gland ( Fig. 3 ). The branches of facial nerve were not involved by the tumor, and the facial nerve monitor (Nerve Integrity Monitor, Medtronic, Minneapolis, MN) was used intra-operatively to facilitate nerve identification and minimize the risk of nerve injury. Postoperatively, transient facial nerve weakness (Grade II House-Brackman Grading System) was observed and it resolved after 3 months. On final histopathologic analysis, diagnosis consisted of cribriform adenoid cystic carcinoma ( Fig. 4 ), surgical margins were negative for tumor involvement, with no perineural infiltration. The CT scan follow-up was performed 6 months after surgery, and it confirmed the total removal of the lesion.
