鋸歯状腺管の組織学的検討ならびに過形成ポリープとserrated adenomaの鑑別

Histological Analysis of the Serrated Glands and Differential Diagnosis of the Hyperplastic Polyp and Serrated Adenoma

要旨　過形成ポリープ（hyperplastic polyp；HP）と鋸歯状腺腫（serrated adenoma；SA）に特徴的な鋸歯状腺管の形態学的特徴を解析した．鋸歯状腺管は，正常腺管の腺管開口部から表層部にかけての上皮細胞の形態変化，すなわち細胞更新の過程を模倣した病変であると考えられた．CEAやKi-67を用いた検討も細胞更新を模倣した病変の見解を支持するものであった．HPとSAの違いは細胞更新を模倣する細胞に分裂能力があるかないかであり，HPでは分裂像は病変の下部に限局し，鋸歯状腺管にはKi-67陽性細胞はほとんどみられない．SAでは分裂細胞は病変全体に分布し，Ki-67陽性細胞は鋸歯状腺管にも観察された．この診断基準で分類されたHPとSAのKi-67陽性率とargyrophilic nucleolar organiser regions（AgNOR）数には有意差が認められた．

　Serrated glands found in hyperplastic polyps (HP) and serrated adenomas (SA) showed characteristic morphological features consisting of tall columnar cells with intraluminal papillary projection and short columnar cells with a concave portion. The luminal contour of these columnar cells depicted the serrated lumen. These columnar cells were similar to those found in the upper part of normal colonic mucosa where successive morphological changes occur in the epithelium from crypt openings to the surface as a terminal process of cell renewal. The tall columnar cells in serrated glands seemed to correspond to the surface epithelium of normal mucosa and short columnar cells correspond to epithelium lining the crypt openings. Immunohistochemical staining using carcinoembryonic antigen and Ki-67, supported the homologous features found in serrated glands and in the superficial part of normal mucosa. Difference between SA and HP was considered to be due to whether the proliferating cells participate in the serrated glands or not. Mitotic figures or Ki-67 positive nuclei were confined to the lower portion of the HP and they were seldom observed in serrated glands. On the other hand, mitotic figures or Ki-67 positive nuclei were scattered throughout the whole area of SA including serrated glands. We calculated the Ki-67 positive rate (Ki-67 PR) and the number of intranuclear dots of argyrophilic nucleolar organizer regions (AgNOR number) in 26 lesions of typical HP and in 38 lesions of typical SA to verify our criteria for differentiation between HP and SA. Significant differences were obtained in both the Ki-67 PR and the AgNOR number of both groups.