隆起型食道腫瘍の鑑別診断―内視鏡の立場から

Endoscopic Differentiation of Protruding and Submucosal Tumor of the Esophagus

要旨　隆起を示す食道腫瘍には，良性および悪性腫瘍が含まれるため，隆起の形（隆起の丈と基部の広さ），周囲粘膜からの立ち上がり，表面の凹凸や表面性状，大きさ，硬さ，色調，上皮内伸展の有無などを参考に鑑別を行う．平滑筋腫と顆粒細胞腫は，上皮で覆われた固い腫瘍を示すのに対し，脂肪腫，リンパ管腫，海綿状血管腫は，緊満感のない軟らかい腫瘍を示しており，色調などを参考にすれば，良性疾患はある程度診断可能である．これに対し，粘膜下腫瘍様の形態を示す食道癌は診断が難しい．発見時点で既に粘膜下層癌であり，血行性転移を生じる傾向があり予後不良のため，治療方針決定のためにも早期の診断が望まれるが，表層に露出している病巣部分が狭いため，適切な腫瘍組織が採取できず，確定診断に至らないこともある．粘膜下腫瘍様の形態を示す食道癌には，低分化型扁平上皮癌，類基底細胞癌，未分化型癌，腺様囊胞癌，腺扁平上皮癌，粘表皮癌などが含まれるとされているが，低分化型扁平上皮癌と類基底細胞癌では，粘膜下腫瘍様以外に，様々な隆起の形態を示す症例があり，形態だけでは診断困難である．

　For the differential diagnosis of protruding esophageal tumors, endoscopic findings such as shape, the height and width at the base of the tumor, mode of elevation such as smooth or sharp, irregularities of the surface, size, color and concomitant mucosal lesions should be observed by conventional observation.

　Leiomyoma and granular cell tumor are solid and hard tumors covered by normal esophageal mucosa. Lipoma, lymphangioma and cavernous hemangioma are soft tumor without strain. Color of tumors should be considered.

　Miscellaneous histological types such as poorly differentiated squamous cell carcinoma, basaloid squamous carcinoma, undifferentiated carcinoma, adenoid cystic carcinoma, adeno-squamous carcinoma and mucoepidermoid carcinoma are frequently identified among superficial and protruding esophageal cancers. They frequently have venous permeation and lymphatic permeation that result in distant organ metastases and poor prognosis. Chemotherapy and/or irradiation are recommended for them other than surgery. Early diagnosis and prompt treatment are mandatory. At the same time, endoscopic differentiation of them from squamous cell carcinoma is difficult, for tumor tissue occupies the subepithelial layer and invade into the submucosa. Bite biopsies should be repeated to get tumor tissues and establish final diagnosis.