直腸カルチノイド腫瘍の画像診断―X線・内視鏡・EUS：転移例と非転移例の比較を中心に

Endoscopic, Radiographic and EUS Diagnosis of Rectal Carcinoid Tumors―Comparison between Metastatic and Non-metastatic Cases

要旨　多施設から集計した直腸カルチノイド114例（119病変）を，転移例（7例7病変）と非転移例（107例112病変）に分け，臨床像，X線，内視鏡および超音波内視鏡（EUS）所見を比較検討した．転移の可能性の指標は大きさ10mm以上，中心陥凹（潰瘍），深達度mp以深であった．転移例と非転移例の画像所見の比較では，内視鏡は陥凹の有無以外に差はみられなかったが，1病変を除き病変は良好に観察できていた．X線は内視鏡に比べ微小な病変（5mm未満）や浅い陥凹では描出困難なものがみられ，側面変形の出現率も低率であったがmp以深の3病変はすべて変形を伴っていた．一方，EUSでは転移例は不均一なエコーパターンを呈する病変が多く，深達度診断（smとmp以深の鑑別）では1例を除き正診されていた．直腸カルチノイドの質的診断では，内視鏡による大きさの推測や陥凹の有無を観察し，EUSにてより正確な腫瘍径と深達度診断を行い，悪性度の指標が認められればX線検査を追加することが有用と考えられた．

　One hundred and fourteen cases (119 lesions) of rectal carcinoid tumors, which included seven cases (7 lesions) with metastatic lesions, were analyzed in order to evaluate the usefulness of endoscopy, radiography and endoscopic ultrasonography (EUS) in the diagnosis of carcinoid tumors with metastatic lesions. As a result of the clinicopathological findings, metastatic factors of rectal carcinoid tumors were considered to be central depression (ulceration) of the tumor surface, a size more than 10 mm and deep tumor invasion beyond the muscularis propria (mp).

　Endoscopic examination was the superior method of observing the surface appearance, especially the shallow central depression. However, there was no significant difference in endoscopic findings between metastatic and non-metastatic cases except for the finding of central depression. Radiologically, some tumors less than 5 mm in size and some cases of shallow central depression were not detected. Basal deformities in the lateral view of the lesion were not so useful for the diagnosis of deeper invasion of the submucosa, but all three tumors invading beyond the mp had basal deformities. On the other hand, in cases with metastatic lesions, EUS showed nonuniform internal echo patterns including internal calcification more often than in cases without metastatic lesions. The diagnosis of depth of invasion (sm or more than mp) using EUS was accurate except in the case of one lesion.

　As for the diagnosis of rectal carcinoid tumors, firstly, endoscopic examination with careful observation of surface appearance was useful, but EUS examination was necessary for the purpose of a more accurate diagnosis of the size and the invasion depth of tumors. Finally, barium enema should be added when metastatic factors are recognized by the former two methods of diagnosis.