低異型度分化型胃癌の自然史

Natural History of Gastric Low-Grade Differentiated Carcinoma

要旨　低異型度分化型胃癌の自然史を明らかにするため，当院で治療された連続する300例の胃癌切除症例における臨床病理学的検討，および低異型度癌成分を含む症例の内視鏡的な遡及的追跡を行った．臨床病理学的には低異型度癌のみからなる腫瘍は，粘膜にとどまるものが大部分であった．低異型度癌成分を含む症例は，粘膜内腫瘍の周辺部に低異型度癌成分が位置するものが多く，粘膜内腫瘍中心部から粘膜下層以深の腫瘍の大部分は高異型度癌成分よりなっていた．27例の遡及的追跡では，すべての症例は粘膜内癌にとどまっており，隆起型，陥凹型にかかわらず腫瘍の発育速度は遅く，年間0.1～0.2mm程度の発育速度であった．低異型度分化型癌は非常に発育速度が遅く，粘膜内である程度の大きさになると高異型度癌成分が発生し，その成分の粘膜下層浸潤が起こると通常の進行癌同様，急速に発育していくと考えられた．

　We performed a clinicopathological study and a retrospective study of endoscopic images of gastric low-grade differentiated carcinoma lesions to investigate the natural history of this disease. Clinicopathologically, most of gastric cancers composed of only low-grade component were limited to the mucosa. For gastric cancers with some low-grade components, most of low-grade components belonged only to the peripheral part of the tumor in the mucosa, but most of the high-grade component existed in the center of the lesion in the mucosa and invaded as far as the submucosa or further. For the 27 cases of the retrospective study of endoscopic images, all cases were mucosal lesions at resection. For both the protruded and depressed lesions, the developmental speed of the tumor in the mucosa was as low as 0.1～0.2mm per year. We conclude that the gastric low-grade differentiated carcinoma is a slow-growing tumor. When the low-grade carcinoma reaches about 3cm in size in the mucosa, high-grade carcinoma component develops from the tumor and invades into the submucosa. As in ordinary advanced carcinoma the tumor then grows rapidly.