食道癌取扱い規約に定義された上皮内腫瘍の病理組織学的検討―食道小扁平上皮癌と上皮内腫瘍

Histopathological Examination of Intraepithelial Neoplasia Defined in the New Guide Lines for the Clinical and Pathological Studies on Carcinoma of the Esophagus

要旨　「食道癌取扱い規約第10版」で新たに定義された上皮内腫瘍を組織学的に検索し，その取り扱い方と問題点を検討した．上皮内腫瘍は癌が疑われる病変であり，胃や大腸の腺腫とは異なるものである．生検標本における上皮内腫瘍の頻度は上皮内癌を除くと1％前後であった．癌が疑われる病変ということから，上皮内腫瘍の診断には上皮内癌の組織診断基準が確立されることが必要である．そして，上皮内癌を高異型度上皮内腫瘍と分けて扱うことが，規約を運用するうえで問題が少ないととらえられた．また，上皮内腫瘍は癌を強く疑うかどうかで亜分類すべきであり，層構造だけでなく，細胞異型所見を合わせて判断することが必要である．

　According to the World Health Organization Classification of Tumours,Pathology and Genetics of Tumours of the Digestive System, intraepithelial neoplasia（IN）of the esophagus was defined in the new guide lines for the clinical and pathological studies on carcinoma of the esophagus. Both definitions are slightly different in the handling of low grade IN. So examined IN histologically, the characteristic and problems of IN are pointed out.

　IN is not benign tumor like adenoma of colorectum and stomach, but atypical epithelium that is doubted cancer. The frequency except of carcinoma in situ（CIS）is around 1%. There are some problems in IN as follows ; 1）the difficulty of morphologic diagnosis of benign tumor, 2）the difficulty of identification of low and high IN and 3）the confusion in diagnosing carcinoma occurred by the removal of CIS from squamous cell carcinoma.

　From the view point that IN is doubted cancer, the diagnostic criteria of CIS is necessary to be established immediately. Then CIS will be diagnosed apart from high grade IN. And IN should be subdivided the degree of doubt cancer, not only by laminar structure of atypical epithelium but also by nuclear atypia.