腺腫内癌を合併した大腸多発性化生性ポリープの1例

Multiple Metaplastic Polyps of the Colon Associated with Adenomas Complicating Focal Carcinoma, Report of a Case

　大腸の化生性ポリープは，結節状の小隆起としてしばしば認められ，特に高齢者において高頻度にみられる．その本態については不明な点が多いが，非腫瘍性の病変で癌化することはないとされ腺腫とは明確に区別されるべき病変と考えられている．しかるに，化生性ポリープが多発することは極めてまれで，内外にわずかの報告をみるにすぎない．最近われわれは，大腸に比較的大きい化生性ポリープが多発すると共に，ほかに粘膜内癌を伴う腺腫を合併した極めて稀有な症例を経験したので，ここに報告する．

　A 54 year-old man came to our hospital with a history of bloody stool. Barium enema examination revealed multiple polyps of the colon and twenty-six polyps were removed by colonoscopic polypectomy, twenty-three of them being retrived. Histological study revealed twenty metaplastic polyps and three adenomas, two of them being associated with focal carcinoma. Metaplastic polyps were located in the sigmoid, the descending and the transverse colon with mean size of 8 mm (2～14 mm) and most of them were pedunculated. It was difficult to differentiate metaplastic polyps from adenomas endoscopically, but magnifying photograph of the removed polyps showed a characteristic“sawtooth appearance”of tubular orifice in metaplastic polyps. Two pedunculated sigmoid polyps were tubulo-villous adenomas histologically, one of which was associated with focal carcinoma. It was interesting to note that the adenoma of the splenic flexure was tubular adenoma which contained three foci of severe dysplasia including atypical goblet cells with a loss of polarity of mucous secretion. At the basis of two of three adenomas metaplastic tubules were present. It has been generally thought that metaplastic polyps are histologically distinct from adenomas and no transition from metaplastic polyps to carcinoma has been encountered. However, like this example, multiple metaplastic polyps may have some malignant potential contrary to the previous concept and may have to be treated as a high risk group of colonic carcinoma.