硬口蓋微小分泌腺癌。最近報告された症例

Microsecretory adenocarcinoma of the hard palate: A case report of a recently described entity.

• Fumi Kawakami
• Toshitaka Nagao
• Yumi Honda
• Junki Sakata
• Ryoji Yoshida
• Hideki Nakayama
• Seijiro Inoue
• Mika Kitajima
• Osamu Ikeda
• Masato Nakaguro
• Yoshiki Mikami

抄録

硬口蓋微小腺癌の1例を報告する。症例は37歳女性で，プライマリケア歯科医が偶然発見した15mmの粘膜下腫瘍が硬口蓋内に発生した．術前の磁気共鳴画像診断では，T2強調画像上で高信号を示す腫瘍が認められ，ダイナミックスタディでは徐々に増強されていた．組織学的には，腫瘍境界は線維性カプセルを伴わない不明確なものであり，腫瘍周囲には小唾液腺が隣接しており，腫瘍周囲には浸透性浸潤が認められた．腫瘍は、多角形の狭い好酸球性から透明な細胞質と小さな均一な楕円形の核を持つ間葉状の管状細胞から構成されていた。これらの細胞は、小嚢胞、尿細管および筋交叉を形成し、淡い好塩基性分泌物および小嚢胞を収集し、豊富な線維筋腫性のストロマを形成していた。腫瘍細胞はCK AE1+AE3、S-100タンパク質、p63に陽性であったが、p40、α-SMA、カルポニンには完全に陰性であった。MEF2C-SS18融合体は、逆転写酵素ポリメラーゼ連鎖反応により同定された。特徴的な組織型，免疫フェノタイプ，MEF2C-SS18融合体の存在から，硬口蓋微小分泌腺癌と診断された．術後の経過は問題なく，術後4ヵ月後には病変は認められなかった．

We report a case of microsecretory adenocarcinoma of the hard palate. The patient is a 37-year-old woman with a 15 mm submucosal tumor, which was incidentally found by her primary care dentist, in her hard palate. Preoperative magnetic resonance imaging revealed a tumor exhibiting high signal on T2-weighted image, which was gradually enhanced on dynamic study. Histologically, the tumor border was ill-defined without fibrous capsule and adjoined minor salivary gland with permeative infiltration at the tumor periphery. The tumor comprised intercalated duct-like cells with polygonal narrow eosinophilic to clear cytoplasm and small, uniform oval nuclei. These cells formed small infiltrative microcysts, tubules and fascicular cords collecting pale basophilic secretions and small vacuoles setting in an abundant fibromyxoid stroma. The tumor cells were positive for CK AE1+AE3, S-100 protein, and p63, while are completely negative for p40, alpha-SMA, and calponin. The MEF2C-SS18 fusion was identified by reverse transcriptase-polymerase chain reaction followed by Sanger sequencing. The combination of characteristic histology, immunophenotype, and presence of MEF2C-SS18 fusion indicated the diagnosis of microsecretory adenocarcinoma of the hard palate, an entity described only recently. Post-operative course was uneventful and there was no evidence of disease at 4 months after surgery.

© 2020 Japanese Society of Pathology and John Wiley & Sons Australia, Ltd.