消化管への転移性腫瘍の診断

Imaging Diagnosis of Metastatic Gastrointestinal Tumors

要旨　消化管の転移性腫瘍のうち，腫瘍塞栓性転移（血行性，リンパ行性転移）を中心に概説した．悪性腫瘍の消化管への転移の頻度は，食道1％前後，胃2.3～6％，小腸1.14～2.9％，大腸1.9％で食道転移の頻度が最も低いと思われた．転移の原発巣は，すべての臓器で肺癌，乳癌の頻度が比較的高く，他には食道では，胃癌，子宮頸癌，舌癌が，胃では食道癌，悪性黒色腫が，小腸では，悪性黒色腫，腎癌が，大腸では，子宮癌，食道癌が多くみられた．症状は，食道では嚥下困難が最も多く貧血がこれに続いた．胃では吐下血，体重減少，嘔気嘔吐が多く，小腸では下血，イレウスが，大腸では腹痛，腹満感，排便困難等，臓器によって特徴的な所見がみられた．転移巣の個数は，多発例は半数以下と少ないが（食道40％，胃47％，小腸34～37％，大腸22％），表面型を呈する大腸転移では83.3％が多発病変であった．形態は粘膜下腫瘍様のみならず，原発の癌や悪性リンパ腫に類似するものもみられ，粘膜下腫瘍様を呈した頻度は半数以下であった（食道40％，胃43％，小腸33.3％，大腸22.2～28.6％）．治療法は手術が基本となるが，他部位に転移を合併している症例も多く，化学療法が施行されることも多い．近年では単発の表面型の転移に対しては，より侵襲の少ない治療法として，polypectomyやEMRを施行して予後の改善を見た症例も報告されるようになってきた．予後は概ね不良であるが，近年は，2年以上の生存例の報告も増えており，早期発見と積極的な治療によって，予後の向上が期待できると思われた．

　Among metastatic tumors, characteristics of true embolic metastasis (hamatoganeous and lymphatic metastasis) were mainly reviewed. Frequency of metastasis of malignant tumors to the gastrointestinal tract is as follows ; esophagus :1％, stomach :2.3～6％, small intestine :1.14～2.9％. Metastasis to the esophagus seemed to the least frequent. As for the origin of metastatic tumor, lung cancer and breast cancer were origins comparatively more frequent in every organ. In addition, gastric cancer, uterine cervical cancer and lingual cancer were origins frequent in the esophagus. Esophageal cancer and malignant melanoma in the stomach, malignant melanoma and renal cell carcinoma in the small intestine, and cervical cancer and esophageal cancer in the colon were frequent. As for clinical manifestation, dysphagea followed by anemia was the most frequent in the esophagus. Hematomesis and melena, weight loss, nausea and vomiting were frequent in the stomach. Melena and intestinal obstruction in the small intestine, and abdominal pain, abdominal distention and dyschezia were frequent in the colon. In a word, various manifestations characteristic to each organ were seen. Less than half of the cases had multiple lesions (esophagus :40％, stomach :47％, small intestine :34～37％, colon22％), however, 83.3％ of colonic lesions of superficial type had multiple lesions. As for macroscopic features, there were not only submucosal tumor-like lesions but lesions resembling the original cancer or malignant lymphoma. Frequency of submucosal tumor-like lesions was less than50％ (esophagus :40％, stomach :43％, small intestine33.3％, colon :22.2～28.6％). The principal therapeutic procedure is an operation, but, as there are many cases having metastasis to other organs, chemotherapy is also frequently employed. Recently, less invasive treatment such as polypectomy or EMR has been employed for solitary metastatic lesions superficial in type, and cases in which progression has been delayed due to such treatment have been reported. Although the prognosis is generally poor, reports of cases who have survived for more than two years have recently increased. Therefore, delay of progression can be expected by early detection and intensive treatment.

　1) Department of Radiology, National Kyushu Cancer Center, Fukuoka, Japan

　2) Department of Pathology, Fukuoka University Chikushi Hospital, Fukuoka, Japan