大腸鋸歯状病変の病理診断

Pathological Diagnosis of Serrated Lesion of the Colorectum

要旨　筆者らは大腸鋸歯状病変を鋸歯状腺腫（SA），過形成性ポリープ（HP），異型過形成性ポリープ（AHP）に分類・診断している．診断基準は主所見（粘膜中層～表層の核偽重層）と2つの副所見（好酸性細胞質，腺管分岐）の組み合わせから成るが，核偽重層と腺管分岐は鋸歯状病変の細胞増殖動態の異常を，好酸性細胞質は杯細胞の分化異常を表現している．欧米では鋸歯状病変をserrated polypと総称し，hyperplastic polyp（HP），sessile serrated adenoma（SSA），traditional serrated adenoma（TSA）に3分しているが，それらは筆者らのHP，AHP，SAにほぼ相当する．大腸鋸歯状病変の病理診断では，筆者らのAHP（欧米のSSA）の位置づけ（腫瘍か非腫瘍か）を明確にすることが最重要課題と考えられる．

　We classify serrated lesion of the colorectum into serrated adenoma (SA), hyperplastic polyp (HP), and atypical hyperplastic polyp (AHP), according to the combination of the major (nuclear pseudostratification in the middle to the upper zone of the crypt) and two minor findings (eosinophilic cytoplasm and glandular branching). Both nuclear pseudostratification and glandular branching reflect the abnormal proliferation and eosinophilic cytoplasm reflect goblet cell immature differentiation. In western countries, serrated lesions are put together as serrated polyp and classified into hyperplastic polyp (HP), sessile serrated adenoma (SSA), and traditional serrated adenoma (TSA), which correspond to the HP, AHP, and SA of our classification, respectively. It is thought most important to elucidate the nature of AHP (or SSA), whether neoplastic or not, for the pathological diagnosis of serrated lesion.