小腸非上皮性腫瘍の分類と画像診断―従来の筋原性腫瘍とGISTとの関連

Classification and Diagnosis of Non-epithelial Tumors of the Small Intestine

要旨　近年，消化管の非上皮性腫瘍の分類にGISTの概念が登場してきた．GISTは免疫染色による分類であり，従来のH・E染色による分類との間に大きな乖離がある。H・E染色で筋原性腫瘍と診断されていた5症例を提示し，GIST分類との関連について検討した．5例すべてがRosai分類による広義のGISTであった．1例はcombined type，1例はneural typeであったが，残り3例はuncommitted type(狭義のGIST)であった．これら症例間に切除標本肉眼像，画像診断での鑑別点はなかった．文献的にも従来の小腸の筋原性腫瘍のほとんどは狭義のGISTであると報告されている．臨床的には従来の筋原性腫瘍の診断をGISTと言い換え，さらに狭義のGISTの可能性が高いと診断すればほぼ問題はなく，臨床的取り扱いも従来の筋原性腫瘍と同じで良いと思われた．

　In recent years, the concept of GIST (gastrointestinal stromal tumor) has appeared in the classification of non-epithelial tumors of the gastrointestinal tract. GIST is a classification made by immunohistchemistry and can show a large deviation from the classifications by the H・E staining method. Five cases diagnosed as smooth muscle tumors by H・E staining were observed and examined, and the diagnoses were compared with the classifications of GIST. All five cases were GIST in the wide sense by Rosai's classification. Although one case was combined type and one case was neural type, the remaining 3 cases were the uncommitted type. Discriminating points in the macroscopic appearance of resected specimens and diagnostic imaging were not observed among these cases. It is reported that GISTs include most tumors previously designated as smooth muscle tumor of the small intestine. For this reason, it is usually satisfactory that tumors diagnosed as conventional smooth muscle tumors are categorized clinically into GIST with the possibility of GIST in the strict sense still being high. It is also thought that clinical management could be the same as that of the conventional myogenic tumors.