特殊な食道悪性腫瘍における内視鏡診断の最前線

Frontiers in Endoscopic Diagnosis of Rare Malignant Esophageal Tumors

要旨●特殊型食道癌の通常内視鏡所見の特徴は，上皮下発育を反映した急峻な立ち上がりを示す上皮下病変様隆起である．特に類基底細胞扁平上皮癌や神経内分泌癌では，表面は非腫瘍性扁平上皮に被覆されることが多く，光沢感を有し平滑である．また拡大内視鏡観察では，非腫瘍性扁平上皮と膨張性発育を示す腫瘍との間に存在するSECN-like vesselsを認めることが多く，口径不同に乏しいnetwork状血管として観察される．時に無色素性悪性黒色腫でも同様の所見を呈する．一方，粘表皮癌や腺扁平上皮癌では，腫瘍が表層に露出あるいは近接する場合，浸潤性発育を反映してType R血管を呈することが多い．癌肉腫や悪性黒色腫では特徴的な形態や色調が診断の契機となる．腺様囊胞癌や未分化癌は極めてまれであり，その内視鏡的特徴については今後さらなる症例の蓄積が望まれる．

　Rare histological esophageal malignancy types often exhibit distinctive endoscopic features reflecting their unique growth patterns. On conventional endoscopy, these tumors frequently present as subepithelial lesion（SEL）-like elevations with a steep marginal rise, reflecting predominant subepithelial growth. Specifically, basaloid squamous cell carcinoma and neuroendocrine carcinoma are commonly covered by non-neoplastic squamous epithelium, culminating in a smooth and glossy surface appearance.

　Usually, magnifying endoscopy reveals characteristic SECN-like vessels located between the non-neoplastic squamous epithelium and the expansively growing tumor. These vessels typically show a network-like pattern with minimal caliber variation. Similar findings may occasionally be observed in amelanotic malignant melanoma.

　In contrast, mucoepidermoid carcinoma and adenosquamous carcinoma frequently manifest Type R vessels when the tumor is exposed at the mucosal surface or located close to it, reflecting their infiltrative growth pattern. Carcinosarcoma and malignant melanoma are relatively easy to recognize endoscopically because of their unique morphology and coloration.

　Because of the rarity of esophageal adenoid cystic carcinoma and undifferentiated carcinoma, their endoscopic features remain insufficiently defined, and additional cases are needed to better characterize their diagnostic features.