十二指腸粘膜下腫瘍の臨床診断と治療

Clinical Diagnosis and Treatment for Duodenal SMT（Submucosal Tumor）

要旨　十二指腸粘膜下腫瘍は比較的まれな疾患である．さらに十二指腸粘膜下腫瘍には臨床的に種々の疾患が含まれ，通常の内視鏡観察のみによる質的診断は容易ではない．内視鏡下生検による病理組織学的検査においても確定診断に至らない場合もあり，診断的治療が行われ切除後に確定診断がなされることも少なくない．最近では日常臨床として一般的に施行される超音波内視鏡（EUS）は，消化管粘膜下腫瘍の診断において非常に有用である．EUSは病変部の断層像が描出可能であり，病変の局在層，形態，エコーレベル，パターンを評価することで粘膜下腫瘍の質的診断が可能となる．また超音波内視鏡下穿刺吸引細胞診（EUS-FNAB）を行うことで消化管壁深部からの組織採取が可能である．十二指腸悪性腫瘍は非常にまれであるが，カルチノイドやGISTなどmalignant potentialを有する疾患もあり，十二指腸粘膜下腫瘍に遭遇した際は小病変であっても通常の内視鏡観察に加えEUSや組織学的検索を行い確定診断に努め，疾患に応じた適切な治療を考慮することが大切である．

　Duodenal SMT（submucosal tumor）is an uncommon disease. As duodenal SMT is included in various diseases, it is difficult to make a correct diagnosis of duodenal SMT only by ordinary endoscopic examination. Furthermore we cannot obtain an appropriate specimen by biopsy study in all cases, because the tumor is located deep in the wall. As a result, duodenal SMT is sometimes confirmed histologically from the diagnostic surgical material. EUS（endoscopic ultrasonography）is very helpful for preoperative diagnosis of SMT of the digestive tract. EUS can reveal the cross-sectional images of SMT. We can make a correct diagnosis of duodenal SMT by analyzing localization, form, echogenicity and echo pattern obtained from EUS images. In addition, we can obtain an appropriate specimen of SMT by using EUS-FNAB（EUS guided fine needle aspiration biopsy）. We can also perform immunohistochemical examination from the specimens obtained by EUS-FNAB.

　Duodenal malignant neoplasm is very rare, but there are some SMT that have malignant potential such as GIST（gastrointestinal stromal tumor）. Therefore, we should attempt to make a correct diagnosis and provide appropriate follow-up strategy, even when SMT is small. To avoid excessive invasive treatment for patients, early detection and adequate treatment are important.