病理からみた微小大腸腺腫―Ki-67，p53および内分泌細胞分化からみた隆起型と表面型腺腫の比較

Immunohistochemical Study on Minute Adenomas of the Large Intestine

要旨　5mm以下の微小大腸腺腫89病変を表面平坦・陥凹型：A群(37病変)，表面隆起型：B群(22病変)，隆起型：C群(30病変)の3型に大別し，3者における増殖能，癌抑制遺伝子産物および細胞分化の異同について比較検討した．Ki-67labeling indexの平均はA群35.6％，B群44.5％，C群55.0％とC群に有意に高かった．増殖細胞の分布様式は，すべての肉眼型において表層に強かったが，C群ではA，B群に比較し全層性に，しかも強くみられる傾向があった．p53蛋白陽性率はA群35.1％，B群59.1％，C群50％であり，C群の2病変で中等度局所性にみられた以外すべて軽度散在性に発現していた．クロモグラニン陽性細胞はA群で75.7％，B群で72.7％，C群で80％にみられた．以上，増殖能を除き癌抑制遺伝子産物と細胞分化の立場からは，表面型と隆起型の微小大腸腺腫間には大きな差はなく，表面型も隆起型と同様の組織診断基準と取り扱いでよいと思われた．

　We compared 89 lesions of minute adenoma (smaller than 5 mm in size) immunohistochemically in cell proliferation, tumor suppressor gene product and cell differentiation. They were classified as follows ; 37 superficial flat and depressed lesions (IIb 21, IIc+IIa 11, IIc 5), 22 superficial elevated lesions (IIa 15, IIa+IIc 7) and 30 protruded lesions (Ip 3, Isp 6, Is 21). The labeling index of Ki-67 was 35.6% in superficial flat and depressed type, 44.5% in superficial elevated type and 55.0% in protruded type, respectively. Ki-67 positive cells were mainly noted in the upper third of neoplastic glands, and were shown more diffusely in protruded type than in superficial type. It is possible for superficial flat and depressed lesions to develop protrudedly. Overexpression of p53 protein was detected in 35.1 f of superficial flat and depressed type, 59.1% of superficial elevated type, and 50% of protruded type, respectively. Also overexpression of p53 protein was detected focally in two lesions of protruded type, and sporadic patterns were detected in others. Chromogranin immunoreactive cells were found in 75.7% of superficial flat and depressed type, 72.7% of superficial elevated type and 80% of protruded type, respectively. These results suggest that there is no remarkable difference between superficial type and protruded type in minute colorectal adenomas except for cell proliferation.