各論③ 副耳下腺腫瘍と診断できずに手術を行った巨大副耳下腺多型腺腫の1例

Diagnosis and Surgical Treatment of Accessory Parotid Gland Tumors

はじめに

　副耳下腺は，正常人の約21～56 ％に存在するといわれている 1），ステノン管に沿って耳下腺約6 mm前方で咬筋上に存在する異所性の耳下腺である 2）。副耳下腺腫瘍は頬部腫瘤を主訴とするため，過去の報告では約1/4の症例が形成外科を受診している 3）。一方，形成外科医は頬部の腫瘍を頻繁に扱うが，副耳下腺腫瘍に対する認識がないと粉瘤などのほかの腫瘍と誤診してしまうことになる。そして，綿密な計画なく手術を行うことで，予期せぬ顔面神経損傷などの合併症を起こす危険がある。

　著者は，術前に副耳下腺腫瘍と診断できずに手術を行ったが，十分な準備を整えて手術に臨んだことで，安全に手術を行うことができた巨大副耳下腺多型腺腫の1例を経験した。この症例を振り返って，診断と手術に関して文献的考察を加え報告する。

　I describe the case of a gigantic pleomorphic adenoma of an accessory parotid gland which could not be diagnosed before surgery. Patients with mid-cheek masses often visit a plastic surgery clinic; such mid-cheek masses may arise from any type of soft tissue. Although these masses can originate from an accessory parotid gland, accessory parotid gland tumors are extremely rare, and their diagnosis can be difficult. If plastic surgeons are not aware of the possibility of an accessory parotid gland tumor, this tumor might be misdiagnosed or a facial nerve might be damaged during surgery, or the tumor’s resection might be inadequate. To help avoid such situations, I provide details regarding the diagnosis and treatment of accessory parotid gland tumors. For the evaluation of accessory parotid gland tumors, a CT scan is important to determine the anatomical location. MRI images accurately reflect the cellular density and tumor components. For a cytological diagnosis, fine-needle aspiration cytology provides valuable information. The common surgical approaches to an accessory parotid gland tumor include a parotidectomy incision and a mid-cheek incision. The parotidectomy incision is widely advocated because of its lower risk of facial nerve injury. However, a mid-cheek incision has some advantages, although some authors have proposed that this incision be conducted only by experienced surgeons, as a facial nerve may be excised by this approach. To avoid the risk of facial nerve injury, surgeons should choose the most suitable approach depending on the size of the tumor.