組織形態計測に基づく大腸絨毛状腫瘍の異型度の評価と良性悪性判別

Morphometric Analysis of Atypia Grading of Colorectal Villous Tumors

要旨　大腸絨毛状腫瘍の良性悪性を客観的に振り分けるために，それを対象として，2つの異型度係数（ING，ISA）とそれから導かれる判別式について検討を行った．絨毛状腫瘍のING平均値は良性腺管腺腫のそれに近く，ISA平均値は管状腺癌のそれよりも高かった．それらの分布をISA-ING相関図上でみると，良性腺管腺腫と管状腺癌の分布域の間の領域を中心に分布していた．また，それらは良性腺管腺腫・管状腺癌の計測値から得られた二変量線形判別関数Fによりその約70％が悪性に判別された．これらのことから，絨毛状腫瘍の組織構造は悪性としての構造異型の1つであると考えられる．明らかな悪性絨毛状腫瘍の計測値と管状腺癌のそれとの間に差があることから，異型度係数の重みづけを変えずに両者の平均値の差だけFを平行移動して，それを絨毛状腫瘍の新しい良性悪性組織診断基準とすると，絨毛状腫瘍の計測値の95％は悪性に判別された．

　Fifty cases of villous tumors were evaluated regarding atypia grading by means of computer-aided histological morphometry. Two indices (ING and ISA) were defined to quantify cellular and structural atypia of the villous tumors. The ING is a kind of N/C ratio and the ISA represents density of glands.

　The mean value of ING and ISA for villous tumors were 42.5±8.07 and 88.8±3.97, respectively. The mean value of ING was similar to that for tubular adenomas and the mean value of ISA was greater than that for adenocarcinomas (Table 2). The correlation diagram of ISA and ING showed that the values for villous tumors were distributed in the borderline area between tubular adenomas and adenocarcinomas. The linear discriminant function (F) obtained from the ING and ISA values for tubular adenomas and adenocarcinomas was applied to 106 fields of 50 villous tumors. Seventy percent of them were discriminated as malignant (Fig. 3). It was thought that the discriminant function (F) should be shifted to the benignancy side, taking into consideration the index values of definitely malignant villous tumors and large villous tumors (more than 5 cm in size)(Table 3). The shifted discriminant function (Fv) was capable of classifying 95% of 106 fields of 50 villous tumors as malignant (Figs. 4 and 5).

　Based on these results, villous structures should be regarded as one of the structural atypia of malignant epithelial tumors of the colorectum.