非結節集簇様大腸腫瘍の1例―その形態学的特徴像と遺伝子背景

“Non-nodular Type” in Lateral Spreading Tumor, Report of a Case

要旨　患者は70歳の男性．早期胃癌の手術目的で当センターに入院となった．術前注腸検査で表面型隆起性病変を指摘された．注腸・内視鏡検査で腫瘍は約30mmの極めて丈の低い平滑な表面隆起型腫瘍で，その腫瘍辺縁が外に凸の“花弁状”，ないしは“偽足様”所見を呈していた．腫瘍は一部に隆起成分を持ちsm浸潤を疑った．切除した結果，33×25mmのsm₁の高分化腺癌＋高度異型腺腫であった．sm浸潤は多中心性で，組織異型度は，癌との鑑別が困難な腺管が連続性に混在していた．p53の免疫染色で腫瘍全体に過剰発現を認め，K-rasの点突然変異は認めなかった．本症例と同じ表面型隆起で，腫瘍辺縁に筆者らが呼唱する“偽足様”所見を有する腫瘍群といわゆる結節集簇様腫瘍とをp53の免疫染色とK-rasの点突然変異について検索した結果も合わせて報告する．

　A 70-year-old man was admitted to have an operation for early gastric cancer. During the examination of the colon before the operation, a superficial tumor was detected. Barium enema and endoscopic examinations showed a flat elevated tumor, 30 mm in size, at SD junction. The shape of the margin of this tumor was like that of an amoebae with protruding edges. Examination of the resected specimen showed that the macroscopic diagnosis was flat elevated type, 33 mm in diameter with slight sm invasion. From the characteristics of the surface and edge's shape, we have proposed that this type of superficial tumor to “Non-nodular type” lateral spreading tumor. Overexpressions of p53 were detected all over this tumor, K-ras Codon 12 point mutations were not detected and APC LOH yolded no information. “Non-nodular type” was compared with “Nodular type” called Nodular-aggregating tumor in p53 overexertions and K-ras point mutations. Overexpressions of p53 were seen in 61% (11/18 cases) in “Non-nodular type” and 34% (10/29 cases) in Nodular type respectively. In addition, “Non-nodular type” were stained diffusely all over the tumor in spite of histology and Nodular type were stained focally in coincidence with the cancer. K-ras mutations were seen in 0% (0/18 cases) and 60% (24/40 cases) respectively. These characteristics of Non-nodular type were compatible with those of superficial depressed tumor.